Upload
others
View
18
Download
0
Embed Size (px)
Citation preview
CorrosionProtection
Textbook
Version:�3.3
©�2001�-�2014�Inter-Industry�Conference�On�Auto�Collision�Repair
CPS01-STMAN1-E
This�page�is�intentionally�left�blank.
Corrosion�ProtectionTextbook
Table�of�Contents 3
Contents
Introduction..............................................................................................................................7Obligations�To�The�Customer�And�Liability.......................................................................... 7
Module�1�-�Corrosion�Origins�And�Prevention.......................................................................13Causes�Of�Corrosion...........................................................................................................13OEM�Corrosion�Protection..................................................................................................14Preventing�Corrosion�During�Repairs..................................................................................19Module�Wrap-Up............................................................................................................... 26
Module�2�-�Corrosion�Protection�During�Repairs................................................................... 29Cleaning..............................................................................................................................29Part�Preparations................................................................................................................. 31Joining�Surfaces.................................................................................................................. 33Primers................................................................................................................................36Aerosols.............................................................................................................................. 40Seam�Sealers.......................................................................................................................41Chip-Resistant�Coatings...................................................................................................... 47Module�Wrap-Up............................................................................................................... 51
Module�3�-�Corrosion�Protection�After�Repairs.......................................................................55Anti-Corrosion�Compound..................................................................................................55Undercoating...................................................................................................................... 57Module�Wrap-Up............................................................................................................... 59
Module�4�-�Vehicle�Maker�Recommendations....................................................................... 63OEM�Warranties................................................................................................................. 63Vehicle�Maker-Specific�Recommendations......................................................................... 63Module�Wrap-Up............................................................................................................... 72
This�page�is�intentionally�left�blank.
Introduction
This�page�is�intentionally�left�blank.
IntroductionTextbook
Corrosion�Protection 7
Obligations�To�The�Customer�And�Liability
The�collision�repair�industry�has�anobligation�to�correctly�repair�thecustomer’s�vehicle.�Collision�repairs�mustbe�performed�using:
• recommended�or�testedprocedures�from�vehicle�makers,I-CAR,�and�other�research�andtesting�organizations.
• quality�replacement�parts�andmaterials.
• repair�processes�and�parts�aswritten�and�agreed�upon�in�therepair�order.�If�items�on�the�repairagreement�are�not�consistentwith�the�repair�order,�it�can�beconsidered�fraud.
Performing�proper�collision�repairsrequires�using�parts�and�procedures�thatkeep�remaining�warranties�intact.
Collision�repairs�must�restore:
• safety.• structural�integrity.• durability.• performance.
• fit.• finish.
Throughout�the�damage�analysis�andrepair�process�the�repairer�and�insurermust:
• communicate�with�each�other.• maintain�constant�communication
with�the�customer.• be�in�agreement�with�each�other
and�the�customer�on�how�repairswill�be�performed.
• inform�the�customer�of�anychanges�in�the�repair�plan�fromthe�original�repair�agreement,�andexplain�the�changes�and�why�theyhave�to�be�made.
To�reduce�liability:
• make�sure�that�all�repairs�areperformed�thoroughly,�correctlyand�as�listed�in�the�damage�report.
• follow�proper�procedures.• have�documentation�of�required
repairs�with�detailed�recordkeeping�available�for�customers.
IntroductionTextbook
Corrosion�Protection 8
Technicians�are�considered�theexperts�and�are�expected�to�beknowledgeable�on�how�to�performa�quality�repair.
Liability�insurance�that�covers�the�repairfacility�may�not�always�cover�all�damages.For�example:
• the�policy�may�not�coverfaulty�repairs,�leaving�liabilityresponsibility�completely�on�thefacility.
• a�shop�owner�may�find�that�repairfacility�liability�coverage�may�notcover�the�full�amount�awarded�ina�lawsuit.�The�shop�owner�wouldhave�to�pay�the�difference.
It�is�difficult�to�reduce�the�risk�of�liabilityexposure.�The�part�that�the�repairer�cancontrol�is�the�chance�of�being�found�atfault.�Chances�can�be�minimized�by:
• using�recommended�or�testedprocedures�from�the�vehiclemakers,�I�CAR,�or�other�researchand�testing�organizations.
• using�quality�replacement�partsand�materials�that�restore�fit,
finish,�durability,�and�perform�atleast�as�well�as�the�original.
• keeping�thorough�records.
Keeping�thorough�records�includes�morethan�recording�the�date,�mileage,�and�pre-existing�damage.�Record�keeping�alsoincludes:
• making�sure�all�notes�are�legible.• verifying�the�repairs�that�were
made�or�not�made.• having�the�customer�sign�a
waiver�for�repairs�that�they�donot�want�performed.�Repairersmust�determine�their�liability�onnot�repairing�safety�systems�suchas�restraint�and�anti-lock�brakesystems.
• keeping�computer�printouts�orworksheets�on�file�showing�wheelalignment�readings�or�vehicledimensions�before�and�afterrepairs.
• keeping�scan�tool�printouts�andrecords�of�computer�codes�forairbag,�anti-lock�brake,�emission,and�powertrain�control�module(PCM)�systems.
IntroductionTextbook
Corrosion�Protection 9
• attaching�the�OEM�or�other�testedprocedure�printout�to�the�vehiclerepair�order.
• keeping�receipts�for�all�subletwork�performed.
Refer�to�"Video:�Topics�Off�Limits"�in�thepresentation.�This�video�identifies�topicsthat�should�not�be�brought�up�in�class.
This�page�is�intentionally�left�blank.
Module�1�-�CorrosionOrigins�AndPrevention
This�page�is�intentionally�left�blank.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 13
Causes�Of�Corrosion
Learning�objectives�for�this�moduleinclude:
• describing�the�causes�of�corrosion.• listing�steps�OEMs�take�for
corrosion�protection.• describing�how�to�prevent
corrosion�during�repairs.
Refer�to�“Video:�Importance�Of�CorrosionProtection”�in�the�presentation.�Thisvideo�discusses�some�of�the�reasons�whyrestoring�corrosion�protection�is�vitalduring�the�collision�repair�process.
The�formation�of�corrosion�like�this�requires�acombination�of�exposed�metal,�oxygen,�and�anelectrolyte.
Corrosion�is�an�electrochemical�reactioncalled�oxidation�that�is�formed�whencombining�exposed�metal,�oxygen,�andan�electrolyte,�such�as�acids,�salts,�ormoisture.
A�snow-covered�road�like�this�likely�has�added�roadsalt,�one�of�the�main�corrosion�promoters.
Elements�that�promote�corrosioninclude:
• road�salt�and�magnesium�chloride,both�used�to�melt�snow�and�iceon�roads.�Some�states�and�regionshave�found�that�salt�is�not�effectivein�very�cold�temperatures,�somagnesium�chloride�is�beingsubstituted�as�a�deicer.�It�is�alsoused�as�a�dust�control�agent�onunpaved�roads�in�some�states�andregions.�Magnesium�chloride�isapplied�as�a�liquid.�It�is�highlycorrosive�when�wet,�and�sticks�tometal�surfaces�better�than�salt.
• acid�rain.• pollutants.• moisture.• collision�damage,�which�breaks
coatings�and�exposes�bare�metal.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 14
• improper�collision�repairs,�suchas�when�repaired�surfaces�are�nottreated.
The�exposed�metal�in�this�one�spot�is�a�classicexample�of�a�corrosion�hot�spot,�where�corrosionforms�faster�than�other�areas�not�exposed.
Corrosive�hot�spots:
• are�so-named�because�theyare�exposed�metal�areas�whichcorrode�faster�than�other�areasnot�exposed.�Corrosion�canstart�instantly�in�some�cases,�acondition�known�as�flash�rustingwhich�is�typically�visible.
• may�be�a�spot�with�a�broken�paintfilm.
• may�be�separated�weld�joints.• may�be�damaged�anti-corrosion
coatings.
OEM�Corrosion�Protection
Refer�to�"Video:�OEM-Applied�CorrosionProtection”�in�the�presentation.�This�videodiscusses�some�of�the�coatings�applied�atthe�factory�for�corrosion�protection.
This�featheredge�profiles�the�different�coatingsapplied�by�the�OEM.
Corrosion�protection�materials�appliedduring�the�vehicle�original�buildinclude:
• a�zinc�coating�at�the�steel�mill.• metal�treatment.• an�electrodeposition�coating�(E-
coat)�process.• seam�sealers.• chip-resistant�coating.• topcoats.• undercoating.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 15
This�illustrated�graph�shows�that�zinc�is�more�activethan�steel,�which�is�why�zinc�is�used�for�sacrificialcorrosion�on�steel�panels.
A�coating�of�zinc�on�the�steel:
• is�applied�at�the�steel�mill�beforethe�steel�is�delivered�to�the�vehiclemakers.
• protects�the�steel�with�“sacrificial”corrosion.�This�is�a�type�ofcorrosion�that�is�not�destructive.The�more�chemically�active�metal,zinc,�oxidizes�and�forms�a�tightbond�that�does�not�flake�off,�thusprotecting�the�steel�underneath.
• is�called�“galvanized”�and�byvarious�other�names�dependingon�the�coating�process.�The“galvannealed”�process�iselectroplated�and�heated�to�forma�zinc-iron�alloy.�The�processof�“electrolytic�galvanizing”�iswhere�sheet�steel�is�moved�past�apositively�charged�zinc�plate.�Zincis�applied�to�the�sheet�steel�withthe�help�of�electricity.�Still�anotherprocess�is�“hot�galvanizing,”where�steel�is�dipped�into�a�hotzinc�bath.
Refer�to�Module�1,�“Demonstration:�Zinc-Coated�Coupon”�in�the�presentation�for�anexample�of a�zinc-coated�coupon.
The�body-in-white�goes�through�a�series�of�washingsand�rinses�to�prepare�the�surface�for�OEM�primer.
One�of�the�first�treatments�of�the�stampedand�assembled�vehicle�“body-in-white”at�the�vehicle�assembly�plant�is�metaltreatment,�which�may�be�up�to�an�eleven-step�process�that�includes�a:
• hot�detergent�wash�and�rinse,which�removes�grease,�oil,�etc.
• phosphoric�acid�wash,�whichremoves�scale�and�opens�poresin�the�metal.�A�rinsing�stepneutralizes�the�acid.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 16
• zinc�phosphate�acid�treatment�andrinse,�which�applies�a�layer�of�zinccrystals.�The�body�is�then�bakeddry�to�remove�excess�moisturefrom�cracks�and�crevices.
This�process�prepares�the�body�for�theadhesion�of�the�electrodeposition�coating,or�E-coat.
GM�C/K�Pickup�Bed
The�olive-drab�color�on�this�GM�pickup�bed�iselectrodeposition�coating,�or�E-coat.
The�E-coat�process:
• charges�the�body�and�coatingwith�opposite�charges.�Thisvaries�by�vehicle�maker,�alsoreferred�to�as�original�equipmentmaker,�or�OEM.�If�the�vehiclebody�is�negatively�charged�andthe�coating�positively�charged,it�is�called�“cationic�(CAT-ee-on-ik)�electrodeposition.”�If�thebody�is�positively�charged,�it�iscalled�“anionic�(AN-ee-on-ik)electrodeposition.”�The�oppositecharges�ensure�full�coverage�anduniform�thickness.
• fully�immerses�the�body�in�thecharged�coating,�allowing�the
coating�to�reach�areas�that�a�spraygun�cannot�reach.
• coating�is�a�gray,�brown,�or�olivedrab�color,�depending�on�thevehicle�maker.
Saturn�Ion
Seam�sealers,�like�this�sprayed�bead�on�the�inner�rearbody�panel,�are�typically�applied�by�robots.
Seam�sealers�are:
• designed�to�eliminate�moistureand�air�intrusion�wherever�panelsjoin.
• mostly�applied�by�robots,�thoughthere�are�some�locations�on�thevehicle�where�seam�sealers�areapplied�by�hand.
Seam�sealers�are�applied�at�this�stagebecause�most�seam�sealers,�on�theexterior�at�least,�are�topcoated.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 17
Chevrolet�Sonic
Textured�chip-resistant�coatings�are�most�commonon�the�lower�part�of�the�rocker�panel.
A�chip-resistant�coating:
• is�designed�to�cushion�the�impactof�stones�and�debris�from�the�road.
• is�applied�typically�to�lower�areasvulnerable�to�stone�chips,�such�asthe�bottom�of�the�rocker�panel.
• may�be�visible,�especially�on�someAsian�and�European�makes�andmodels�where�the�coating�is�atextured�surface�that�is�easy�to�see.This�is�most�prevalent�beneath�therocker�panel�and�may�be�on�thelower�door�skin.�A�chip-resistantcoating�may�not�even�be�a�coatingat�all,�but�an�applied�plastic�sheet.
• may�not�be�visible,�includingnon-textured�coatings�applied�toupperbody�areas�such�as�the�frontof�the�hood�and�sometimes�thefront�of�the�roof.�These�coatingsare�detectable�only�with�a�filmthickness�gauge.
Lexus�HS�250h
The�final�topcoat�layer�is�clearcoat,�which�gives�thevehicle�its�showcase�appearance.
Topcoats,�including�basecoat�andclearcoat,�are�not�officially�part�of�thecorrosion-protection�steps�but�do�play�arole�in�the�protection.�The�basecoat�doesnot�generally�have�corrosion-inhibitingproperties,�but�the�clearcoat:
• prevents�breakdown�of�the�finish.• protects�against�ultraviolet�rays.• protects�against�road�splash,�acid
rain,�etc.
Honda�Accord
The�vehicle�maker�may�add�anti-corrosioncompounds�to�inner�cavities,�such�as�inside�rails.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 18
The�next�step,�at�least�for�somevehicle�makers,�is�applying�anti-corrosion�compounds.�Anti-corrosioncompounds�are�typically�applied�after�thetopcoats�have�been�applied�to�preventcontamination�of�the�finish.�Anti-corrosioncompounds�are:
• generally�wax-based�coatings.• applied�to�cavities,�such�as�inside
rails,�the�bottoms�of�door�shells,and�inside�rocker�panels.
Ford�Mustang
Most�vehicle�makers�apply�a�layer�of�stone-resistantundercoating�to�the�inner�wheelhouse.
A�textured�undercoating:
• is�typically�applied�in�thewheelhouse�areas.
• may�be�applied�under�the�floorpan.�European�vehicle�makers�aremore�likely�to�apply�undercoatingunder�the�floor�pan.�Other�vehiclemakers�consider�the�E-coat�to�beadequate�chip�protection�for�mostof�the�underbody.
• provides�resistance�to�corrosionand�also�vibration�and�wear.
• may�vary�in�thickness�and�color.• is�usually�petroleum-based,�but
some�are�wax-based.
Audi�Q5
One�of�the�variations�of�corrosion�treatment�ishow�boron-alloyed�steel�is�protected.�Audi�uses�analuminum�/�silicon�coating,�such�as�on�this�Q5.
Besides�the�application�of�undercoating,there�are�other�variations�among�vehiclemakers�on�the�corrosion�protectioncoatings�applied.�These�include�the:
• composition�of�the�phosphatecoating.
• amount�of�chip-resistant�coating.Also,�the�appearance�of�chip-resistant�coating�varies�betweenvehicle�makers�and�vehiclemodels.
• number�of�topcoats.• application�of�anti-corrosion
materials.�European�vehiclemakers�are�more�likely�to�applyanti-corrosion�compounds�thanother�vehicle�makers.�All�vehiclemakers�require�anti-corrosioncompounds�to�be�applied�duringrepairs.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 19
• coatings�to�boron-alloyed�steel.Some�vehicle�makers,�such�asFord,�Audi,�and�Jaguar,�haveboron-alloyed�steel�coated�with�analuminum�/�silicon�coating,�whichresists�the�heating�and�quenchingprocess.�BMW�prefers�boron-alloyed�steel�be�zinc-coated,�thesame�as�any�other�steel,�for�betterweld�quality.�Still�other�vehiclemakers�leave�this�ultra-high-strength�steel�uncoated.
Toyota�Venza
OEM�service�parts�receive�the�same�treatment�as�therest�of�the�full�body,�but�the�E-coat�is�commonly�auniform�black.
OEM�coatings�on�service�parts�are�exactlythe�same�as�applied�to�entire�vehiclebodies,�in�that:
• the�steel�parts�begin�with�zinc-coated�steel�at�the�steel�factory.
• there�is�the�same�full-submersionwash,�rinse,�and�phosphatetreatment.
• there�is�a�full-submersion�E-coatand�baking�process.�The�onlydifference�with�service�parts�is
that�the�coating,�in�the�end,�iscommonly�a�uniform�black.
Some�parts�may�be�prepared�and�coatedusing�an�outside�supplier,�but�thesesuppliers�are�held�to�the�same�standardsfor�materials,�treatment,�and�corrosion-resistance.
Preventing�Corrosion�During�Repairs
Honda�Accord
Restoring�corrosion�protection�during�repairs�mayinclude�applying�anti-corrosion�compound�incavities�to�treat�repair�backsides.
Restoring�corrosion�protection,�andpreventing�corrosion�from�occurringduring�the�repair,�should�be�a�priority�foreveryone�involved�in�the�repair�process.
Coatings�applied�by�vehicle�makers�mustbe�restored�during�repairs:
• where�the�coatings�have�beendisturbed�or�removed.�Neglectingcorrosion�protection�can�causecorrosion�to�form�under�a�paintfilm�or�in�an�area�where�chippedpaint�occurs.
• because�the�steps�and�coatingsapplied�by�vehicle�makers�arethere�for�a�reason.�There�are�no
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 20
unnecessary�steps�done�on�theassembly�line�or�paint�line�at�avehicle�assembly�plant.
• because�if�not�restored,�corrosiondamage�will�occur.�The�corrosionmay�only�be�a�visible�annoyancein�some�areas,�but�it�speaks�to�thequality�of�the�repair�process.
Not�addressing�corrosion�protection�during�repairscan�lead�to�failure�of�the�structure,�like�on�this�lowertie�bar.
If�corrosion�protection�is�not�restored:
• there�will�likely�be�prematurefailure�of�the�part�or�panel.
• there�may�be�weakening�ofstructural�parts�or�even�failureof�the�vehicle�structure.�Hiddencorrosion�in�a�structural�area�cansacrifice�impact�protection�in�acrumple�zone.
• the�repair�facility�will�be�facedwith�comebacks�and�held�liablefor�any�injuries.�Comebacks�dueto�corrosion�cost�time,�money,reputation,�and�future�businesslost.
Volvo�S40
It�is�important�to�preserve�the�E-coat�as�much�aspossible,�such�as�removing�the�coating�only�wherenecessary�for�spot�welds,�rather�than�the�entireflange.
It�is�important�to�preserve�the�E-coat�whenrepairing�a�vehicle.�The�E-coat:
• is�the�most�effective�corrosion-inhibiting�coating�that�is�applied�tothe�vehicle.
• should�not�be�broken�throughexcept�where�it�is�required�orspecifically�recommended.Examples�are�in�the�weld�zonesand�on�structural�adhesiveapplication�areas.�Structuraladhesive�requires�bare�metal�foradhesion,�and�has�corrosion-inhibiting�properties�forprotection.
• can�be�kept�mostly�intact�by�notgrinding�an�entire�flange.�Forexample,�on�uniside�replacements,for�reasons�of�speed�it�is�temptingto�remove�all�of�the�coatingson�the�mating�flange,�not�justthe�weld�areas.�Not�grindingthe�entire�flange�will�also�helpprotect�the�zinc�coating,�whichalso�should�not�be�removed�unlessrecommended�by�the�vehicle
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 21
maker.�The�zinc�coating�will�likelybe�gone�from�the�original�weldsites�on�a�vehicle�flange,�butrefrain�from�removing�the�coatingon�the�replacement�panel.
• should�generally�be�kept�intacton�inserts�used�for�making�GMA(MIG)�butt�joints.�When�making�aninsert,�choose�the�E-coated�metalwhen�possible,�which�will�alsoinclude�an�intact�zinc�coating.Remove�the�E-coat�only�where�theweld�will�be�made.
Volvo�S40
The�grinding�process�creates�heat,�forming�moisturewhen�the�metal�cools,�which�is�a�corrosionpromoter.
Heat�is�a�promoter�of�corrosion,�whetherapplied�during�the�grinding�process,�whenGMA�(MIG)�welding,�or�directly�witha�heat�source.�When�heat�is�applied,the�metal�gets�hot�and�then�cools.�Thisforms�condensation,�or�moisture,�whichaccelerates�corrosion.
The�corrosion-acceleration�processworsens�with�every�heat�application.
Notice�how�the�coatings�on�the�backside�of�thepanel�have�been�burned�away�from�the�stud�weldingprocess.
Not�remembering�the�backside�is�a�waythat�technicians�may�be�causing�corrosionwithout�knowing�it.�Backsides�of�a�repairmay�not�be�visible,�but�if�not�addressed,corrosion�will�form�and�eventually�will�bevisible.
Backsides�of�repairs�are�importantbecause�most�processes�done�on�the�frontside�also�affect�the�backside.�Examplesinclude:
• GMA�(MIG)�welds�along�flangesor�seams.�The�heat-effect�of�aGMA�(MIG)�weld�removes�boththe�E-coat�and�zinc�coating�on�thebackside,�leaving�the�area�open�tocorrosion.
• areas�where�picks,�hammers,�anddollies�were�used.
• anchor�clamp�sites.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 22
Refer�to�Module�1,�“Demonstration:Untreated�Backside”�in�the�presentationfor�an�example�of�an�untreated�backsidesample.
Honda�Pilot
Paintless�dent�repair�requires�pushing�a�dent�outfrom�the�backside,�which�may�disturb�the�backsidecoatings.
Besides�the�examples�already�mentioned,the�backside�of�a�paintless�dent�repair�is�acommonly�missed�backside�area.�Paintlessdent�repair:
• as�the�name�implies,�is�a�processof�removing�shallow�dents�whilenot�disturbing�the�integrity�of�thefinish.�Using�plastic-tipped�picktools,�the�technician�gently�pushesthe�dent�out�from�the�backsidewith�a�lever-type�action.�If�therepair�is�done�right,�no�panelrefinishing�is�required.
• requires�backside�access,�and�thataccess�must�be�existing.
• may�cause�an�issue�with�thebackside�even�if�the�front�sidedoes�not�require�refinishing.During�this�process,�it�is�possiblethat�the�E-coat�or�wax-basedcoating�on�the�backside�of�thepanel�was�removed�from�therepeated�scratching�of�the�denttool�tips,�even�though�the�tipsmay�be�protected�with�plastic.Therefore,�corrosion�protectionmust�be�restored�to�ensure�thedurability�of�the�repair.�This�isrecommended�for�most�PDRrepairs,�as�it�is�difficult�to�see�if�thecorrosion�protection�was�removed.It�is�better�to�assume�that�the�finishhas�been�scratched�and�applycorrosion�protection�to�the�panelbackside.
This�coupon�example�shows�the�issue�with�stud�weldsites.�Even�though�the�stud�tab�is�removed�from�thefront�side,�corrosion�can�still�form�on�the�backsideand�must�be�addressed.
Another�common�example�where�therecould�be�a�backside�corrosion�problemis�a�stud�weld�site.�The�stud�welder�tabis�pulled�off,�the�stud�mark�evidence
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 23
is�removed�from�the�front�side,�but�thebackside�is�ignored.�These�must�be�treatedsimilar�to�the�site�of�a�weld�joint.�Thisprocess�may�even�leave�a�hole�where�thestud�weld�was�pulled�off,�which�should�bewelded�shut.
Honda�CR-V
A�typical�recommendation�for�treating�the�backsideof�a�repair�is�applying�anti-corrosion�compound�witha�wand�through�existing�holes.
To�protect�the�backside�of�repairs:
• clean�the�weld�and�dent�repairbacksides,�if�there�is�access.
• apply�corrosion-resistant�primer,if�there�is�access�for�cleaning.Primers�require�a�clean�surfacefor�proper�adhesion.�Corrosion-resistant�primer�need�only�beapplied�to�areas�where�the�E-coatwas�disturbed.
• apply�anti-corrosion�compounddirectly�to�bare�metal�if�there�is�noaccess�for�cleaning.
Lower�hem�flanges�and�pinchwelds�are�often�trapsfor�collecting�water�and�will�corrode�from�the�insideif�the�backside�surfaces�are�not�treated�during�orafter�repairs.
Lower�hem�flanges�and�pinchwelds�areareas�where�problems�could�occur�ifcorrosion�protection�is�not�considered,due�to�water�collecting�in�these�areas.�Forexample:
• the�bottom�hem�flanges�in�a�doorpanel�form�pockets�that�holdmoisture�and�provide�a�perfectenvironment�for�the�forming�ofcorrosion�from�the�inside.�Theseareas�must�be�treated�after�repairwith�an�anti-corrosion�compoundto�prevent�formation�of�a�corrosivehot�spot.
• lower�pinchweld�flanges,�such�ason�the�bottom�of�rocker�panels,must�be�protected.�Anti-corrosioncompounds�have�creepingcapabilities�that�protect�theseareas.
• drain�holes�may�get�crushed�whentorquing�anchoring�clamps.�Thedrain�holes�are�on�the�bottom�ofthe�rocker�panel.�If�left�closed,�awater�pocket�and�corrosion�willform.�Pry�open�these�drain�holesafter�straightening.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 24
The�simple�act�of�touching�bare�metal�with�barehands�will�cause�corrosion�to�form,�such�as�seenhere�on�this�sample�panel�that�was�subjected�to�asalt�spray.
Touching�bare�metal�with�bare�hands:
• leaves�moisture,�salt,�and�othercontaminants.�This�leads�tocorrosion,�even�after�the�metal�iscoated.
• must�be�cleaned�after�touching.• can�be�avoided�by�wearing�gloves.
Galvanic�corrosion�will�form�whenever�twodissimilar�metals�are�left�in�contact�with�each�otherwithout�a�coating�or�hardware�isolator�betweenthem.
Galvanic�corrosion�forms�when:
• two�dissimilar�metals�come�incontact�and�an�electrolyte�isadded.
• a�steel�bolt�or�rivet�is�used�tofasten�an�aluminum�panel�andthere�are�no�coatings�or�isolators,such�as�a�special�washer,�used�toseparate�the�dissimilar�metals.
Refer�to�Module�1,�“Demonstration:Galvanic�Corrosion”�in�the�presentationfor�an�example�of�a�galvanic�corrosionsample.
Audi�A8
Preventing�galvanic�corrosion�simply�means�beingconscious�of�what�the�vehicle�maker�used�to�isolatethe�dissimilar�metals,�such�as�this�rubber�fastener.
To�prevent�galvanic�corrosion:
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 25
• duplicate�the�original�fastenerinstallation.�This�may�include�theuse�of�special�washers,�spacers,or�other�isolators�replaced�inthe�proper�order�as�done�by�thevehicle�maker.�These�are�designedto�ensure�there�is�no�contactbetween�dissimilar�metals,�such�asaluminum�and�steel�or�magnesiumand�steel.
• insulate�parts�made�from�dissimilarmetals�using�gaskets,�non-metallicwashers,�and�paint�coatings.�Atleast�one�product�maker�(PPG)�hasa�product�in�a�squeeze�tube�thatcan�be�applied�to�fasteners�anddrilled�holes�to�prevent�galvaniccorrosion.�The�product,�ECK(Electrolysis,�Corrosion,�Kontrol),is�formulated�with�zinc.
• drill�required�holes�beforeapplying�coatings.
• replace�coated�fasteners�if�thecoating�is�damaged.�Most�of�thesefasteners�are�one-time�use�for�thisreason.
Jaguar�XJ
When�removing�steel�rivets�that�join�aluminumpanels�by�grinding�or�a�sander,�it�is�importantto�clean�out�steel�shavings�that�might�collect�onthe�interior�cavity.�One�way,�as�shown�here,�is�tovacuum�the�shavings�as�they�are�being�made.
Another�way�to�avoid�galvanic�corrosionis�to�be�aware�when�removing�self-piercing�rivets�on�aluminum-intensivestructures.�With�this�situation:
• self-piercing�rivets�are�coatedsteel.
• removal�may�include�drilling�orpressing�out�or�grinding�the�rivets,which�leaves�steel�shavings�insidealuminum�rails�or�other�cavities.
• it�is�advisable�to�keep�the�cavityclean�by�using�a�vacuum�whilegrinding�or�vacuuming�out�asmuch�of�the�shavings�as�possibleafter�grinding.
• coat�enclosed�interiors�with�anti-corrosion�compound.
Module�1�-�Corrosion�Origins�And�PreventionTextbook
Corrosion�Protection 26
This�course�will�address�corrosion�protection�in�twostages,�during�repairs�in�Module�2,�and�after�repairsin�Module�3.
This�course�will�approach�the�restorationof�corrosion�protection�as�two�stages:
1. During�repairs,�up�through�therefinishing�process,�which�will�bethe�subject�of�Module�2.
2. After�repairs,�including�addingprotection�to�inner�cavities,wheelhouses,�and�underbodyareas,�which�will�be�the�subject�ofModule�3.
Some�of�the�procedures�that�will�becovered�in�the�next�two�modules�are�donein�the�repair�bay�and�some�are�done�inthe�refinishing�area.�Again,�corrosionprotection�must�be�on�all�the�minds�ofeveryone�involved�in�the�repair�process.
Module�Wrap-Up
Topics�discussed�in this�moduleincluded:
• the�causes�of�corrosion.• steps�the�OEM�takes�for�corrosion
protection.• how�to�prevent�corrosion�during
repairs.
Module�2�-�CorrosionProtection�During
Repairs
This�page�is�intentionally�left�blank.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 29
Cleaning
Learning�objectives�for�this�moduleinclude:
• cleaning�a�part�in�preparation�forcorrosion�protection�coatings.
• preparing�an�OEM�service�part,non-OEM�replacement�part,�and�asalvage�replacement�part.
• treating�joining�surfaces.• applying�primer-surfacer,�primer-
sealer,�self-etching�primer,�andepoxy�primer.
• applying�seam�sealers.• applying�chip-resistant�coatings.
Refer�to�“Video:�Part�Preparation”�in�thepresentation.�A�critical�step�for�corrosionprevention�during�repairs�is�making�suremetal�surfaces�are�clean.�This�videoshows�preparation�steps�for�an�OEM�part,aftermarket�part,�and�a�recycled�part.
The�first�step�with�mechanical�cleaning�may�begrinding�welds�(left),�and�may�even�include�spotblasting�(right).
Personal�SafetyProtect�yourself�when�grinding�or�sandingby�wearing�safety�glasses�or�a�faceshield,�leather�gloves,�and�a�particulaterespirator.
A�critical�step�for�corrosion�preventionduring�repairs�is�ensuring�metal�surfacesare�clean.�After�straightening�and�beforeany�joining�processes,�the�existingsurfaces�and�the�replacement�part�surfacesmust�be�cleaned�of�contaminants.Cleaning�is�a�two-part�process,�includingmechanical�cleaning�and�chemicalcleaning.
Mechanical�cleaning�may�include:
• grinding,�only�to�dress�GMA�(MIG)welds.
• sanding�using�various�grits.�Theleast�aggressive�approach�is�best.Start�with�the�finest�grit�that�willdo�the�job,�then�move�to�finer�gritsas�recommended.
• sand�or�media�blasting�whenentire�coatings�are�being�removed.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 30
One�product�maker,�PPG,�has�issued�astatement�that�soda�bicarbonate�blastingis�not�a�good�process�for�cleaning�partsthat�will�be�refinished.�PPG�did�surfaceanalysis�in�areas�of�adhesion�loss,�andfound�that�no�matter�how�well�thetechnician�cleans�the�substrate�after�sodablasting,�there�always�seems�to�be�smallareas�in�the�surface�with�soda�residue.This�usually�causes�adhesion�issues�forthe�next�paint�layer.�If�that�does�not�occur,there�are�paint�defects�that�occur�later�on.Sand�blasting�or�media�blasting�did�nothave�the�same�effect.
More�information�on�blasting�processescan�be�found�in�the�live�I-CAR�“SurfacePreparation�and�Masking�(REF02)”�trainingcourse.
Chemical�cleaning�may�include�a�solvent�orwaterborne�product,�both�shown�here.
Personal�SafetyProtect�yourself�when�using�chemicals�bywearing�safety�glasses�or�goggles,�nitrileor�rubber�gloves,�and�a�vapor�respirator.Follow�the�specific�product�safety�datasheet�(SDS)�for�more�specific�personalprotection.
Chemical�cleaning�may�include�a:
• waterborne�cleaner.• wax�and�grease�remover.�Follow
the�paint�maker’s�directions�for�thepaint�system�being�used.
When�cleaning�with�either�a�solvent�or�waterbornecleaner,�wipe�it�off�in�one�direction�before�it�starts�todry.
To�use�solvent�or�waterborne�cleaners:
• apply�liberally,�keeping�the�surfacewet�to�float�the�contaminants.
• wipe�with�a�clean�cloth�inone�direction�before�it�startsto�dry.�This�will�help�ensurethat�contaminants�are�carriedaway�with�the�cloth.�No�residuemust�remain,�or�it�will�affect�theadhesion�of�the�primer�coat.
• turn�the�cloth�after�each�pass.
Reclean�if�bare�metal�contacts�skin.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 31
Part�Preparations
Preparing�an�OEM�replacement�part�may�includelightly�sanding�the�surface�with�a�soft�backup�pad�toremove�minor�defects.
Replacement�parts�must�be�prepared�forcorrosion�protection�application�beforeand�during�the�repair�process.�Thesesteps�may�vary�depending�on�if�the�partis�an�OEM�replacement�part,�non-OEMreplacement�part,�or�recycled�part.
With�an�OEM�replacement�part:
• most�have�E-coat�applied.• the�part�should�be�thoroughly
cleaned�and�dried.• exposed�surfaces�that�will�be
topcoated�are�scuffed.�It�is�notnecessary�to�scuff�the�backsideor�underside�that�is�not�exposedto�direct�sunlight�or�were�notoriginally�painted�by�the�vehiclemaker.
• inspect�for�damage.�Determinewhat�repairs�should�be�made.�Toremove�minor�defects,�lightly�sandwith�a�dual-action�(DA)�sanderusing�P400�grit�on�a�soft�backuppad,�removing�as�little�E-coat�aspossible.
• primer-sealer�is�applied.�Thisensures�the�color�coat�andclearcoat�have�good�adhesion�andchip�resistance.�Another�benefit�isbetter�color�coverage.
To�test�for�E-coat,�rub�the�surface�with�a�solvent-soaked�cloth�and�look�for�coating�transfer�to�thecloth�or�softening�of�the�coating.
It�is�a�good�practice�to�test�replacementparts�for�E-coat.�The�coating�may�be�ashipping�coating,�which�is�a�temporarycoating�used�on�some�non-OEM�parts.A�shipping�coating�may�even�have�beenapplied�to�an�OEM�part�that�was�returnedand�restocked.
To�determine�if�the�coating�is�E-coat,�do�asolvent�test�or�rub�by:
• rubbing�the�coating�with�a�clothsoaked�in�solvent.
• seeing�if�the�coating�wipes�off�orsignificantly�softens.�If�so,�removeall�of�the�coating�and�apply�acorrosion-resistant�primer.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 32
Chemical�cleaning�of�aluminum�or�magnesium�parts,such�as�this�aluminum�fender,�is�similar�to�cleaningsteel�parts.
The�steps�for�preparing�a�bare�andrepaired�aluminum�or�magnesiumpart�are�similar�to�bare�steel�andrepaired�steel,�at�least�as�far�as�chemicalcleaning�is�concerned.�There�are�somespecial�considerations�for�sanding�andmechanical�tools,�including:
• do�not�use�grits�coarser�than�80.Both�aluminum�and�magnesiumscratch�very�easily.
• oxidation�forms�quickly�onbare�aluminum.�The�rate�variesdepending�on�temperature�andhumidity�levels.�After�beingcleaned�and�left�uncoated�for�anextended�period�of�time,�the�oxidecoating�may�need�to�be�removedagain.
• keep�aluminum,�magnesium,�andsteel�metal�finishing�tools�andsanding�materials�separated�toavoid�galvanic�corrosion.�Crosscontamination�from�the�sandingdust�from�the�different�metals�willcause�galvanic�corrosion�to�occur.This�will�cause�premature�metaldamage�and�paint�failure.
Inspect�a�recycled�part�for�excessive�film�build�byusing�a�film�thickness�gauge�on�various�spots.
When�preparing�a�recycled�replacementpart:
• wash�the�part�thoroughly�withsoap�and�water,�rinse,�and�dry.Follow�that�by�cleaning�with�waxand�grease�remover.
• inspect�for�excessive�film�build,damage,�and�corrosion.�Repairany�damage.
• sand�with�600�grit�wet�or�dry�byhand�or�500�grit�with�a�DA�sanderand�a�soft�backup�pad.�Scuff�theedges�and�recesses�to�remove�allgloss.
• apply�primer-surfacer,�if�thereare�scratches�or�chips�in�originalfinish.�Apply�primer-sealer�to�theentire�part.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 33
Joining�Surfaces
Weld-through�primer�is�available�as�both�an�aerosoland�brush-on�product.
Joining�surfaces�can�be�the�source�ofcorrosion�hot�spots�if�not�adequatelytreated.
After�straightening�and�cleaning�weldmating�surfaces,�a�weld-through�primeris�often�applied�for�corrosion�prevention.Weld-through�primer:
• is�designed�to�be�used�for�bothGMA�(MIG)�weld�and�spot�weldmating�surfaces.�This�includes�buttjoint�inserts,�when�the�insert�is�notE-coated.
• is�heat-resistant,�so�it�will�not�burnaway�during�the�welding�processas�much�as�other�coatings�would.
• may�be�zinc�or�copper�based.Claims�of�95%�zinc�or�coppercontent�mean�that�95%�of�thecoating�left�after�the�primer�hascured�is�zinc�or�copper.
• is�available�as�a�spray�or�brush-on.• is�not�a�good�base�for�topcoats.
Any�excess�weld-through�primershould�be�cleaned�off�beforeapplying�other�coatings.
• may�need�to�be�dry�to�the�touchbefore�welding.�Some�can�bewelded�when�the�coating�isstill�tacky.�For�example,�3Mweld-through�primer�needsto�be�dry�before�welding.�TheSherwin-Williams�Shield�“thin-film�technology”�product�can�bewelded�while�still�tacky.
Apply�weld-through�primer�to�clean,�bare�matingsurfaces�in�the�weld�area.
Weld-through�primer:
• is�applied�to�clean,�baremetal�surfaces�that�cannot�beprotected�by�primer�or�anti-corrosion�compound.�These�areasinclude�flanges�and�inserts�orreinforcements�that�are�flush�withthe�part.
• should�not�be�applied�too�thick.One�thin�coat�of�brush-on�or�twolight�coats�of�aerosol�are�oftenrecommended.�Applying�toomuch�will�increase�resistance�tothe�welding�process�resulting�inexcess�heat�and�weld�spatter.
• should�be�removed�from�the�weldzone�before�GMA�(MIG)�welding.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 34
Welding�through�weld-throughprimer�may�cause�porosity�in�theweld.�This�requirement�may�notbe�clearly�stated�on�the�productcontainer�or�even�the�product�datasheet.
• varies�by�the�amount�that�burnsaway�when�a�GMA�(MIG)�weld�ismade.
Refer�to�Module�2,�“Demonstration:Zinc�Weld-Through�Primer�On�MatingSurfaces”�in�the�presentation�for�anexample�of�zinc�weld-through�primer�onmating�surfaces.
Refer�to�Module�2,�“Demonstration:No�Weld-Through�Primer�On�MatingSurfaces”�in�the�presentation�for�an
example�of�no�weld-through�primer�onmating�surfaces.
There�is�also�copper�weld-through�primer�availablefrom�some�suppliers�that,�like�zinc�weld-throughprimer,�still�burns�away�from�the�weld�site�whenGMA�(MIG)�welded.
Copper�weld-through�primer:
• has�a�higher�melting�temperaturethan�zinc-based�primer,�thoughthere�is�still�some�that�burns�awaywhen�making�a�GMA�(MIG)�weld.
• is�available�from�several�productmakers,�including�InternationalEpoxies�and�Sealers�(IES),�KentIndustries,�and�U-POL.
As�of�the�development�of�this�course,copper-based�weld-through�primer�isnot�recommended�by�any�vehicle�maker,though�some�vehicle�makers�do�notspecify�zinc-based�weld-through�primer.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 35
Refer�to�Module�2,�“Demonstration:Copper�Weld-Through�Primer�On�MatingSurfaces”�in�the�presentation�for�anexample�of�copper�weld-through�primeron�mating�surfaces.
Refer�to�“Video:�Chrysler�On�Weld-Through�Primer”�in�the�presentation.Not�all�vehicle�makers�recommendweld-through�primer.�Chrysler�does�notrecommend�the�use�of�weld-throughprimer�when�repairing�their�vehicles.�Thisis�a�short�video�interview�with�ChryslerCollision�Repair�Manager�Doug�Craigon�Chryslers�decision�to�not�recommendweld-through�primer�for�repairs.
GMC�Sierra
Adhesive�bond�mating�surfaces�requires�removing�allcoatings,�including�the�zinc,�for�adhesion.�Adhesiveis�being�applied�to�this�pickup�boxside.
Adhesive�bond�mating�surfaces:
• usually�requires�removing�all�ofthe�coatings,�including�the�zinc,down�to�bare�metal�for�the�bestadhesion.�Heavy�grinding�shouldbe�avoided,�as�this�would�thin�themetal�and�create�too�much�heat.
• require�adhesive�to�be�applied�toboth�flanges�to�cover�all�the�baremetal,�as�the�adhesive�containscorrosion�inhibitors.
• may�also�be�spot�welded,�in�aprocess�called�weld�bonding.Weld-through�primer�is�not�usedon�weld-bonded�flanges.�It�is�notnecessary�because�of�the�corrosioninhibitors�in�the�adhesive,�and�theresulting�ring�around�the�spot�weldserves�as�a�seal�from�moisture�andair.
More�information�on�adhesively�bondedjoints�and�weld�bonding�can�be�foundin�the�I-CAR�live�“Adhesive�Bonding(ADH01)”�training�course.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 36
Refer�to�Module�2,�“Demonstration:Corrosion-Inhibiting�Adhesive�Sample”in�the�presentation�for�an�example�of�acorrosion-inhibiting�adhesive�sample.
Ford�Mustang
Dressing�GMA�(MIG)�weld�areas�requires�grindingflush�with�the�surface.
Personal�SafetyProtect�yourself�when�dressing�weldsby�wearing�safety�glasses�or�a�faceshield,�leather�gloves,�and�a�particulaterespirator.
When�dressing�GMA�(MIG)�welds�on�thejoint�areas:
• grind�the�weld�flush�with�thesurface.�Use�the�smallest�disc�andfinest�grit�for�the�size�of�joint�orspot�welds.
• ensure�no�porosity�remains,�asthese�cavities�in�the�weld�can�trapcontaminants�and�be�a�source�forcorrosion.
• clean�the�backsides,�as�much�asaccess�allows.
Primers
Refer�to�“Video:�Epoxy�And�Self-EtchingPrimer”�in�the�presentation.�This�videodiscusses�epoxy�primer�and�self-etchingprimer.
Chrysler�300
Primer�has�just�been�applied�to�this�Chrysler�300front�lower�rail�extension�that�was�replaced.
Primer�coatings:
• include�epoxy.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 37
• include�self-etching.• include�primer-surfacer /�primer-
sealer.• must�be�applied�to�a�cleaned
surface.�If�there�is�no�accessfor�mechanical�and�chemicalcleaning,�primers�will�not�adhereto�the�surface.
Two-part�epoxy�primer�is�available�in�largecontainers�for�mixing,�and�also�as�an�aerosol.
Epoxy�primer:
• may�require�an�etching�base,or�can�go�direct�to�metal.�Anetching�base�is�a�two-step�processof�applying�a�metal�cleanerand�conversion�coating,�whichchemically�etches�the�surface.This�process�is�most�often�done�onrestoration�projects,�rather�than�inproduction�repair�facilities.
• may�be�recommended�underplastic�filler�by�some�vehiclemakers.�Toyota�recommendsepoxy�primer�over�bare�steelbefore�body�filler.�This�is�becausewhen�fillers�are�applied�over�thetype�of�zinc�coating�process�usedby�Toyota,�the�filler�material�will
not�adhere�adequately.�Blisteringor�peeling�may�result.
• may�be�one-�or�two-part.�Two-part�primers�use�a�catalyst�to�curerather�than�evaporation�of�solvent.One-part�epoxy�primers,�or�epoxyesters,�are�not�prominent�in�thecollision�industry.
• includes�a�two-part�aerosol.�Two-part�aerosols�have�a�limited�shelflife�once�tapped.
Refer�to�Module�2,�“Demonstration:Epoxy�Primer�Corrosion�Sample”�in�thepresentation�for�an�example�of�an�epoxyprimer�corrosion�sample.
Epoxy�primer�is�commonly�applied�with�a�spray�gunon�large�surfaces�such�as�this�fender.
Application�of�epoxy�primer:
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 38
• requires�cleaning�with�wax�andgrease�remover.
• requires�sanding�the�repair�areaand�cleaning�again.�Follow�theproduct�maker�recommendationsfor�the�finest�grit.�Sanding�withtoo�fine�of�a�grit�will�decrease�thequality�of�primer�adhesion.
• is�typically�done�with�a�spray�gun.
Self-etching�primer�is�also�available�in�various�forms,including�aerosol�and�a�pen�applicator.
Self-etching�primer:
• contains�a�phosphoric�acid,�whichneutralizes�as�it�dries.�Once�theprimer�has�flashed,�the�acid�willnot�react�with�other�coatings.
• may�be�one-�or�two-part.• may�be�in�the�form�of�a�hand-held
marker�or�pen�that�applies�etchingprimer�as�easy�as�stroking�a�pen.
• when�applied,�leaves�a�thin�layerthat�only�etches�the�surface.�Self-etching�primers�do�not�form�abarrier�like�epoxy�primers�andwould�eventually�break�down.�Forthis�reason,�self-etching�primermust�be�coated�with�a�primer-
surfacer�or�primer-sealer.�Washprimers�are�a�form�of�self-etchingprimer�that�is�even�thinner�whenapplied.
• if�applied�too�thickly,�may�inhibitthe�cure.
Refer�to�Module�2,�“Demonstration:�Self-Etching�Primer�vs.�No�Sealer�Corrosion”in�the�presentation�for�an�example�of�aself-etching�primer�vs.�no�sealer�corrosionsample.
Self-etching�primer�is�being�applied�to�this�fender.
When�applying�self-etching�primer:
• start�by�cleaning�the�surface,�justas�with�epoxy�primers.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 39
• sand�the�surface�and�cleanagain.�Follow�the�product�makerrecommendations�regardingsanding�grits.�On�a�spot�repair,the�usual�featheredge�area�is�3"around�the�repair�area.
• use�a�spray�gun.• coat�with�a�primer-surfacer�or
primer-sealer.
Application�of�self-etching�primer�must�be�followedby�a�coating�of�primer-surfacer�or�primer-sealer,�suchas�shown�here.
Personal�SafetyDo�not�expose�eyes�or�skin�to�directUV�light.�Use�UV�safety�glasses(polycarbonate)�available�from�the�lampmanufacturer.�UV�lamps�get�very�hot�andshould�be�kept�away�from�solvent�fumes.Avoid�burns�to�the�skin.
Urethane�primer-surfacer�or�primer-sealer:
• helps�level�out�the�surface�fortopcoat�application.
• is�the�last�step�before�applyingtopcoats.
• may�be�last�step�for�some�hiddenareas�that�do�not�need�topcoat.
• may�be�tinted,�which�sets�a�colorwhen�using�translucent�basecoats.A�tinted�surfacer�or�sealer�will�alsomake�chipping�of�the�finish�lessnoticeable�in�the�long�term.
• may�be�direct-to-metal.�Sherwin-Williams�has�a�direct-to-metalprimer-surfacer,�but�only�foruse�on�a�spot�repair�that�is�5"in�diameter�or�smaller.�A�repairgreater�than�that�diameter�mustfirst�have�self-etching�primerapplied�before�the�primer-surfacer.
• is�also�available�as�an�aerosol�fromsome�product�makers,�and�as�anultraviolet�(UV)-cured�productfrom�some�product�makers.�PPGhas�a�UV-cured�primer-surfacer.
Primer�can�be�applied�to�interior�surfaces�only�ifthe�surface�is�cleaned,�and�one�way�to�do�that�is�bycleaning�and�priming�the�interior�before�enclosing�it.
Due�to�the�cleaning�requirement�forprimer�coatings,�it�may�be�advantageous,even�recommended,�to�apply�primerto�portions�of�a�panel�that�will�not�beaccessible�after�installation.�For�example,treat�the�backsides�of�quarter�panels�andother�areas�that�may�be�difficult�to�accesseven�with�wand�applicators.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 40
After�applying�this�primer�coat,�this�windshieldpinchweld�will�be�masked�before�applying�topcoats.
Stationary�glass�pinchwelds�are:
• the�flanges�where�glass�is�installed.• masked�after�applying�the�primer
coat.�The�exception�is�Audi,�whichrecommends�all�topcoats�beapplied�to�the�glass�pinchwelds.�Atleast�one�vehicle�maker,�Toyota�/Lexus,�recommends�only�epoxyprimer�be�applied�to�stationaryglass�pinchwelds,�and�not�self-etching�primer.�Toyota�/�Lexus�alsorecommends�using�epoxy�primeron�scratches�on�the�pinchweldafter�removing�the�adhesive,�andnot�pinchweld�primer,�which�isnot�a�corrosion-inhibiting�primer.
More�information�on�stationary�glasspinchweld�preparation�can�be�found�inthe�live�I-CAR�“Stationary�Glass�(GLA02)”training�course.
Aerosols
Refer�to�“Video:�Thin-Film�Technology”in�the�presentation.�This�video�discussesthin-film�technology�weld-throughprimer�and�anti-corrosion�compound,�acompletely�aerosol�system.
Refer�to�Module�2,�“Demonstration:�Thin-Film�Technology�Corrosion�Sample”�in�thepresentation�for�an�example�of�a�thin-filmtechnology�corrosion�sample.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 41
Aerosols�are�available�for�most�corrosion�protectioncoatings�such�as�self-etching�primer�and�chip-resistant�coating.
Aerosols�are�a�simpler�way�of�applyingmaterial�compared�to�applying�thematerial�with�a�spray�applicator�gun.Aerosols�are�not�only�available�for�mostcorrosion�protection�materials,�but�quitecommon.�Aerosol�materials:
• are�common�for�small,�spotrepairs.
• may�include�wands�that�can�beattached�to�the�spray�tip�thathave�360°�applicator�tips.�Thewands�may�be�able�to�be�soakedin�solvent�and�reused.
• are�available�for�weld-throughprimer,�self-etching�primer,�epoxyprimer,�anti-corrosion�compound,and�undercoating.
• may�require�more�product�to�beapplied�than�when�using�a�sprayapplicator�gun,�but�this�dependson�the�product.�Some�aerosolsmust�be�thinned�to�allow�them�toatomize�as�an�aerosol.
Seam�Sealers
Refer�to�“Video:�Application�Of�SeamSealers”�in�the�presentation.�This�videodiscusses�the�application�of�seamsealers.
Honda�Accord
Seam�sealers�are�applied�to�seams,�such�as�thisupper�rail�lower�pinchweld.
The�purpose�of�seam�sealers�is�to:
• reduce�the�chances�of�corrosion�ina�flange�and�in�joints.�The�purposeis�NOT�to�fill�in�gaps�or�poorlyfitted�joints,�but�to�complete�theseal�on�the�joint.
• seal�out�moisture�andcontaminants�from�these�joiningareas.
• stop�water�and�air�leaks.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 42
• prevent�fumes�from�entering�thepassenger�compartment.
• reduce�wind�and�road�noise.
Seam�sealers�also�add�to�the�appearanceof�the�seam.
Toyota�Corolla
Even�though�likely�applied�by�a�robot,�this�seamsealer�appears�as�if�it�was�hand-applied�with�a�brush.
Seam�sealers�are�used,�for�example:
• on�a�welded�seam�where�leakagecould�be�an�issue.
• on�closure�panel�openings.• around�lamps.• in�the�engine�compartment,
including�on�the�cowl,�aroundstrut�towers,�and�the�apron-to-lower�rail�joint.�Any�seamsealer�will�work�for�underhoodapplications.�Epoxy-,�urethane-,and�solvent-based�seam�sealersare�all�resistant�to�gasoline,�oil,and�other�fluids�and�can�takeunderhood�temperatures.
• on�floor�pans.• on�quarter�panels.• around�the�fuel�filler�neck.
Solvent-based�seam�sealers�shouldnot�be�used�around�the�fuel�filler
neck�where�there�likely�is�directexposure�to�splashed�fuel.
Seam�sealers�are�available�in�many�forms,�colors,and�makeup�to�allow�the�best�match�of�the�originalapplication.
There�are�numerous�types�of�seam�sealers,including:
• epoxy.• urethane.�Urethane�seam
sealers�are�one-part�and�curewhen�exposed�to�moisture�andheat.�They�have�no�solvents�toevaporate,�so�can�be�paintedimmediately�and�baked�withoutthe�risk�of�solvent�popping.�Thesesealers�should�not�be�tooled�witha�solvent,�which�would�preventcross-linking.
• thin-bodied,�which�are�lowviscosity�and�self-leveling.
• heavy-bodied,�which�have�a�highviscosity.�Heavy-bodied�seamsealers�are�good�on�vertical�jointsbecause�they�do�not�run�whenapplied.�There�are�also�sealersconsidered�medium-bodied�andsemi-self-leveling.
• sprayable.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 43
• tape.
Refer�to�Module�2,�“Demonstration:�SeamSealer�Samples”�in�the�presentation�for�anexample�of�seam�sealer�samples.
This�seam�sealer�has�some�similar�characteristics�asany�other�seam�sealer.
All�seam�sealers�have�some�commoncharacteristics.�All�seam�sealers:
• are�paintable,�though�some�are�notrefinished�as�they�are�not�seen.
• have�good�adhesion.• are�flexible.• are�non-shrinking.
All�seam�sealers�have�a�shelf�life,�sopay�attention�to�the�born�date�and�use-by�date�to�ensure�all�of�the�desirablecharacteristics�are�still�effective.
Different�seam�sealers�also�have�varyingcharacteristics�to�best�match�the�original�application.
There�are�varying�characteristics�of�seamsealers�as�well,�including�that�they�may:
• be�one-�or�two-part.• be�non-sagging�when�first�applied.• have�variable�cure�time.�Product
makers�say�to�think�about�seamsealers�as�a�topcoat�in�regards�tothe�time�window�after�applyingprimer.�In�other�words,�do�notapply�a�seam�sealer�before�theminimum�cure�time�of�the�primeror�after�the�maximum�cure�time.
• be�colored�or�clear.• have�an�odor,�such�as�solvent-
based�seam�sealer,�which�shouldnot�be�used�on�joints�that�are�opento�the�passenger�compartment.The�odors�can�linger.�The�odor�canalso�embed�in�cloth�upholstery,carpeting,�and�headliners.�Usea�two-part,�moisture-cure�seamsealer�in�these�areas.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 44
Direct-to-metal�seam�sealers,�available�from�someproduct�makers,�require�a�clean�surface,�but�not�aprimer�base.
Direct-to-metal�seam�sealers:
• require�no�primer�or�sealer�base.• contain�corrosion-inhibitors.• avoid�having�to�move�the�vehicle
to�the�spraybooth�for�primingbefore�applying�the�seam�sealersand�then�moving�back�to�thespraybooth�for�applying�topcoats.
• require�a�clean�surface.�Theseseam�sealers�are�corrosion-inhibiting,�not�corrosion-curing.The�surface�must�be�similarlyprepared�as�for�applying�primerand�topcoats,�including�a�cleansurface.
Examples�of�product�makers�with�direct-to-metal�seam�sealers�include�3M,International�Epoxies�and�Sealers�(IES),and�Lord�Fusor.
Refer�to�Module�2,�“Demonstration:Direct-To-Metal�Seam�Sealer�CorrosionSample”�in�the�presentation�for�anexample�of�a�direct-to-metal�seam�sealercorrosion�sample.
This�type�of�seam�sealer�is�sprayed�on�to�match�aspecific�OEM�look.
A�sprayable�seam�sealer:
• has�a�unique�look�compared�toother�seam�sealers.
• is�typically�applied�to�theunderbody,�wheelhouses,�trunks,and�in�the�engine�compartment,but�can�be�applied�anywhere�tomatch�an�OEM�application.
• is�applied�with�an�air-poweredapplicator�gun.
• has�a�pattern�that�varies�with�twogun�settings.�The�settings�control
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 45
the�amount�of�pressure�appliedto�the�back�of�the�cartridge,�andthe�air�atomization�/�spray�pattern.The�pattern�also�varies�with�thedistance�the�gun�is�from�thesurface,�and�the�air�pressure�goinginto�the�gun.�Age�of�the�product�isalso�a�factor�because�some�sealersbecome�slightly�thicker�as�theyage.�A�final�factor�would�be�thetechnician�technique.
Instead�of�using�new�product�to�maketest�patterns�of�sprayable�seam�sealer,�asksupplier�jobbers�if�they�have�outdatedproduct�they�could�give�you�to�experimentwith.
A�tape�seam�sealer�has�similar�characteristics�aschemical�seam�sealers,�and�is�used�to�match�anoriginal�application�that�may�or�may�not�be�tape.
Tape-type�seam�sealers:
• have�a�neat�appearance.• have�no�fumes,�since�they�are�a
solid�tape.• are�often�used�around�closure
panel�openings,�such�as�arounddoor�frames.
• have�varying�widths.
• are�flexible,�so�they�can�be�routedaround�irregular�surfaces�andcurves.
• require�a�properly�cleaned�surfacefor�the�best�adhesion.
Some�seam�sealers�that�are�applied�as�aputty�then�baked�at�the�factory,�may�bemost�easily�duplicated�with�a�tape�seamsealer.
Refer�to�“Video:�Matching�OEMApplication”�in�the�presentation.�Thisvideo�shows�how�to�match�the�OEMapplication�of�seam�sealers.
The�final�test�on�what�type�of�seam�sealer�to�use�ishow�it�matches�the�OEM�application�on�the�otherside.
The�main�goal�when�selecting�andapplying�seam�sealer�is�to�match�the�OEMapplication�in:
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 46
• appearance,�including�texture�andcolor.�Color�matters�especially�forseam�sealers�that�do�not�have�afinish�applied.
• performance.• function.
To�match�a�seam�sealer,�compare�theapplication�side-to-side.�Matching�mayrequire�practice�on�a�test�panel.
Vehicle�makers�may�recommend�certainbrands�and�have�their�own�part�numbersfor�some�seam�sealer�applications.
Refer�to�“Video:�Adding�Seam�Sealer�ToService�Parts”�in�the�presentation.�Vehiclemakers,�including�Chrysler�and�GM,�haveguidelines�on�applying�seam�sealers�toservice�parts.
Toyota�Highlander�Door
Most�vehicle�makers�require�the�application�of�seamsealer�to�some�service�parts,�such�as�Toyota�on�thisdoor�panel.
Chrysler�and�GM�are�not�alone�in�notapplying�seam�sealer�to�some�serviceparts.�Most�vehicle�makers�apply�seamsealer�to�only�a�portion�of�the�serviceparts�and�many�times,�seam�sealer�is�notapplied�at�all,�especially�to�closure�panelssuch�as�service�hoods,�deck�lids,�anddoors.�These�service�parts:
• are�pulled�from�the�assembly�linebefore�some�or�all�of�the�seamsealer�is�applied.
• must�have�seam�sealer�appliedat�the�service�facility�beforeinstallation.�The�seam�sealer�mustmatch�the�other�side,�and�mayneed�to�match�the�portion�of�seamsealer�that�is�already�applied.
Toyota�/�Lexus�has�a�collision�repairinformation�bulletin,�or�CRIB,�number163,�explaining�the�need�to�apply�seamsealers�on�these�service�parts.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 47
Refer�to�Module�2,�“Demonstration:�CRIB163”�in�the�presentation�for�an�example�ofCRIB�163.
Chip-Resistant�Coatings
Refer�to�“Video:�Application�Of�Chip-Resistant�Coating”�in�the�presentation.This�video�discusses�the�application�ofchip-resistant�coating.
Chip-resistant�coatings�available�for�repairs�havevarious�names�and�colors.
A�chip-resistant�coating:
• may�be�called�chip�guard,�gravelguard,�etc.
• is�usually�applied�under�thetopcoat�in�a�repair�facility,�sameas�the�vehicle�maker,�thoughsometimes�the�material�is�appliedover�the�topcoat.
• may�be�textured.
Honda�Pilot
This�small�plastic�sheet�protector�is�a�chip�guard.
Plastic�sheets�for�chip�resistance�are:
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 48
• applied�on�top�of�the�clearcoatand�similarly�replaced�for�repair.
• applied�like�a�decal.• ordered�as�a�vehicle�maker�part�or
cut�to�fit�from�an�aftermarket�kit.
Lincoln�MKZ�Hybrid
This�chip-resistant�coating�has�a�distinct�line�wherethe�coating�stops.
Thick�applications�of�chip-resistantcoating�may�be�found:
• under�the�rocker�panel.• at�the�base�of�A-pillars.• at�the�bottom�of�doors.• in�the�dogleg�area.
Other�locations�that�commonly�have�anextra�layer�of�primer�or�clearcoat�thatserve�as�a�form�of�chip-resistant�coatinginclude:
• front�of�the�hood.• front�of�the�roof.• on�fenders.• on�pickup�truck�boxsides.
There�may�also�be�aftermarket�chip-resistant�coating�applied�on�the�frontlower�bumper.�Vehicle�makers�do�notapply�chip-resistant�coating�to�the�frontlower�bumper.
Toyota�Tundra
Identifying�a�chip-resistant�coating�may�be�as�simpleas�looking�for�an�exaggerated�orange-peel�effect,such�as�on�this�Toyota�Tundra�lower�door�panel.
Chip-resistant�coatings�may�beidentified:
• using�vehicle�maker�serviceinformation.�There�are�usuallyline�drawings�that�show�wherethe�coatings�were�applied�by�thevehicle�maker�and�where�theyshould�be�applied�during�therepair.
• by�film�thickness.�A�measurementover�12�mils�under�a�rocker�panelor�on�a�door�panel�may�indicatethe�presence�of�chip-resistantcoatings,�though�excessive�filmthickness�may�also�be�body�filler.Look�for�a�consistent�thickness.
• visually.�Some�are�textured,�andmay�be�visible�closeup�as�a�slightvariation�in�the�“orange�peel”�ofthe�finish.�The�plastic�sheets�are
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 49
easily�seen.�Some�chip-resistantcoatings�are�not�visibly�apparent.
The�material�is�chosen�based�on�appearance�andcolor,�of�which�there�are�several�to�choose�from.
When�choosing�the�materials�for�chip-resistant�coatings:
• follow�the�product�or�paintmaker’s�recommendation.�Vehiclemakers�usually�do�not�recommendspecific�brands�of�chip-resistantcoatings.
• color�may�be�a�factor.�The�coatingsare�usually�available�as�clear,black,�or�beige.�Depending�on�thebasecoat�color,�one�color�may�bebest�for�hiding.
• it�may�be�based�on�the�substratecoating.�Chip-resistant�coatingsare�available�for�use�over�acrylicenamel,�synthetic�enamel,�andurethane.
Refer�to�“Video:�GM�On�Chip-ResistantCoatings”�in�the�presentation.�This�videofeatures�a�GM�view�on�application�ofchip-resistant�coating,�including�the�not-so-visible�applications.
A�spray�applicator�gun�can�be�used�for�severalcoatings,�such�as�undercoating.
A�spray�applicator�gun�can�be�usedto�apply�chip-resistant�coatings.�Thecoatings�are�also�available�as�an�aerosol.Appearance�of�the�coating�may�be�afactor,�and�in�order�to�duplicate�thatappearance:
• variances�will�affect�texture,�suchas�air�pressure,�distance,�numberof�coats,�and�speed�of�application.
• make�a�test,�or�let-down�panel,�ifnecessary,�adding�different�coats�at
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 50
each�pass�until�the�proper�look�isachieved.
Refer�to�“Video:�Making�A�Test�Panel”�inthe�presentation.�This�video�shows�oneprocedure�for�making�a�test�panel�beforeapplying�chip-resistant�coating.
Making�a�test�panel�is�handy�to�match�a�specificcoating�that�needs�to�be�blended.
When�making�a�test�panel,�take�note�of:
• the�air�pressure�used.�Waterborneand�low�VOC�materials�requiremore�pressure�to�smooth�out�thetexture.
• the�distance�from�the�panel.As�distance�from�the�surfaceincreases,�so�does�the�texture.
• different�flash�times.• the�number�of�coats.
Save�the�test�panels�for�future�use�whentrying�to�match�the�same�texture.
Toyota�Tundra�Door
The�technician�is�using�the�experience�gained�frommaking�a�test�panel�to�blend�into�the�chip-resistantcoating�on�this�Toyota�Tundra�door.
When�applying�chip-resistant�coatings�tothe�vehicle:
• use�the�experience�gained�duringthe�test�panel�process.
• use�the�proper�masking�toduplicate�the�original�application,which�may�also�have�been�tried�onthe�test�panel.
• the�coating�may�need�to�blendinto�an�existing�coating.�Ablending�solvent�can�be�used�forthis�purpose.
• sanding�may�be�required�to�eitherflatten�the�application�or�taper�intothe�same�or�adjacent�panel.
Module�2�-�Corrosion�Protection�During�RepairsTextbook
Corrosion�Protection 51
Module�Wrap-Up
Topics�discussed�in�this�moduleincluded:
• cleaning�for�part�preparation.• preparing�an�OEM�service�part,
non-OEM�replacement�part,�and�asalvage�replacement�part.
• treating�joining�surfaces.• epoxy�primer,�self-etching�primer,
primer-surfacer,�and�primer-sealer.• seam�sealers.• chip-resistant�coatings.
This�page�is�intentionally�left�blank.
Module�3�-�CorrosionProtection�After
Repairs
This�page�is�intentionally�left�blank.
Module�3�-�Corrosion�Protection�After�RepairsTextbook
Corrosion�Protection 55
Anti-Corrosion�Compound
Learning�objectives�for�this�moduleinclude�determining�where�to�apply�andhow�to�apply:
• anti-corrosion�compound.• undercoating.
Refer�to�"Video:�Application�OfAnti-Corrosion�Compound”�in�thepresentation.�This�video�explainsthe�application�of�anti-corrosioncompound.
Anti-corrosion�compound�is�available�as�an�aerosolor�for�applying�with�a�spray�applicator�gun.
Anti-corrosion�compound�material:
• is�typically�a�wax-based�coating,though�a�coating�using�thin-filmtechnology�is�not�wax-based.
• is�called�several�names�by�productmakers,�including�anti-rust�agent,rust�preventer,�etc.
• is�applied�as�a�fine�mist�with�awand�attached�to�a�special�spraygun�or�an�aerosol�can.
• has�self-healing�capabilities.
Refer�to�Module�3,�“Demonstration:�Anti-Corrosion�Compound�Corrosion�Sample”in�the�presentation�for�an�example�ofan�anti-corrosion�compound�corrosionsample.
Volvo�S60
Application�of�anti-corrosion�compound�typicallyinvolves�using�a�wand�to�reach�inner�surfaces.
Module�3�-�Corrosion�Protection�After�RepairsTextbook
Corrosion�Protection 56
Personal�SafetyProtect�yourself�when�using�chemicals�bywearing�safety�glasses�or�goggles,�nitrileor�rubber�gloves,�and�a�vapor�respirator.Follow�the�specific�product�safety�datasheet�(SDS)�for�more�specific�personalprotection.
Anti-corrosion�compound�application:
• is�usually�done�with�wandattachments�for�access�to�innercavities.�Use�the�access�holes�andopenings�recommended�by�thevehicle�maker.
• requires�avoiding�mechanicalparts.
• requires�clearing�drain�holes�afterthe�material�has�set.�It�may�bedifficult�to�avoid�the�drain�holeswhen�applying�the�material,�dueto�its�flow�and�creep�capabilities.
Ford�Explorer
The�interior�of�a�replaced�upper�rail�is�one�locationfor�anti-corrosion�compound.
Anti-corrosion�compound�is�typicallyapplied�inside�non-visible�areas,�suchas:
• inside�pillars,�rocker�panels,and�rails.�Most�anti-corrosioncompound�has�creepingcapabilities,�which�allows�it�topenetrate�pinchweld�flanges,�suchas�on�rail�flanges�and�the�lowerrocker�panel.
• in�the�bottom�perimeter�of�doorshell�cavities.
• on�the�backsides�of�panel�repairs.• aluminum�cavities,�not�just�steel.
BMW,�for�example,�states�intheir�service�information�thatafter�all�straightening�or�weldingwork�on�aluminum�parts,�thecavities�affected�must�be�sealedwith�a�cavity�protection�agentafter�being�painted.�Jaguar,�in�theservice�information�for�the�all-aluminum�XJ,�states�to�treat�allinterior�surfaces�that�have�beendisturbed�by�repairs.�This�includesall�box�members,�cavities,�anddoor�interiors.
Anti-corrosion�compound�may�berecommended�over�primer,�if�the�surfacecan�be�accessed�for�mechanical�andchemical�cleaning.�Primer�adds�a�layerof�protection.�Epoxy�primer�is�mostrecommended.�Self-etching�primer�couldalso�be�applied,�but�it�requires�a�coatingof�primer-surfacer�or�primer-sealer�over�itbefore�applying�anti-corrosion�compound,whereas�epoxy�primer�is�a�one-stepapplication.
Module�3�-�Corrosion�Protection�After�RepairsTextbook
Corrosion�Protection 57
Spray�wands�may�be�flexible�or�rigid,�straight�tip�orflexed,�and�different�lengths.
Spray�wands�for�applying�anti-corrosioncompound:
• are�available�as�flexible�and�rigid.• come�in�different�lengths.• include�spray�heads�for�a�360°�or
fan�pattern.
It�may�be�difficult�to�monitor�filmthickness�and�coverage,�especially�withthe�flexible�wands.�It�is�recommendedto�spray�some�of�the�material�into�acardboard�box�to�get�an�understandingof�the�direction�of�the�wands�whenspraying.�Rotating�the�wand�several�timesbefore�it�is�removed�helps�obtain�bettercoverage.
Undercoating
Refer�to�“Video:�Application�OfUndercoating”�in�the�presentation.This�video�discusses�the�application�ofundercoatings.
Undercoating�material�is�available�as�an�aerosol�orfor�applying�with�a�spray�applicator�gun.
Undercoating�material:
• is�a�thick�tar-�or�synthetic�rubber-based�material.
• is�applied�to�wheelhouseand�underbody�areas,�asrecommended�by�the�vehiclemaker.�The�bottom�of�the�fueltank�is�another�area�commonlyrecommended�for�undercoatingapplication.
• protects�against�abrasion�fromstone�chips�and�other�road�debris,and�corrosion.
• may�be�solvent-�or�water-based.Solvent-based�undercoatingmay�have�some�wax�to�keepthe�material�flexible�in�coldtemperatures.
• can�be�applied�over�primer.Some�can�be�applied�over�baresteel.�Check�the�product�makerrecommendations.
Module�3�-�Corrosion�Protection�After�RepairsTextbook
Corrosion�Protection 58
• has�varying�thicknesses,�colors,and�consistencies�to�match�theOEM�and�aftermarket�appearance.
Refer�to�Module�3,�“Demonstration:Undercoating�Corrosion�Sample”�inthe�presentation�for�an�example�of�anundercoating�corrosion�sample.
Undercoating�is�a�thick�coating�that�is�resistant�tostones�and�other�road�splash,�such�as�the�coating�onthis�wheelhouse.
Characteristics�of�undercoating�generallyinclude:
• resistance�to�road�splash.• resistance�to�oils�and�solvents.• an�ability�to�creep�into�hard-to-
reach�areas.�Hard-to-reach�areasinclude�flanges�and�under�inserts.The�material�should�be�sprayedat�the�correct�viscosity�to�allow
it�to�flow�through�the�spray�wandwith�the�proper�atomization�forthorough�coverage.
• remaining�flexible�as�the�materialages.
• self-healing.�If�the�material�isscratched,�some�products�will�flowback�into�the�scratched�area.
• serving�as�a�sound�deadener.
Lincoln�Town�Car
This�is�a�special�undercoating�recommended�by�FordMotor�Company�that�is�applied�to�the�outside�offrame�rails,�among�other�areas.
Undercoating�is�applied:
• using�the�product�maker’s�sprayapplication�equipment.
• as�an�aerosol�for�small�spot�repairareas.
Module�3�-�Corrosion�Protection�After�RepairsTextbook
Corrosion�Protection 59
General�recommendations�from�vehicle�makersinclude�keeping�undercoating�away�from�movablemechanical�parts�and�areas�that�have�high�heat,�suchas�exhaust�parts.
Vehicle�makers�are�consistent�in�sayingto�avoid�mechanical�parts�and�highheat�areas�when�applying�undercoating,including:
• brake�system�parts.• exhaust�system�and�related�parts.• suspension�mounting�areas.• emission�parts.• ball�joint�covers.• electrical�connectors.
Module�Wrap-Up
Topics�discussed�in�this�moduleincluded:
• anti-corrosion�compound.• undercoating.
This�page�is�intentionally�left�blank.
Module�4�-�VehicleMaker
Recommendations
This�page�is�intentionally�left�blank.
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 63
OEM�Warranties
Learning�objectives�for�this�moduleinclude:
• explaining�what�is�covered�andnot�covered�in�OEM�warranties.
• listing�the�corrosion�protectionrecommendations�from�differentvehicle�makers.
OEM�corrosion�warranties�are�printed�in�the�owner’smanuals.
OEM�corrosion�warranties�may:
• be�up�to�12�years�and�higher.For�example,�Audi,�BMW,Volkswagen,�and�Volvo�have12-year�unlimited�corrosionwarranties.�Porsche�has�a�42-yearunlimited�corrosion�warranty.
• be�unlimited�mileage�or�a�setnumber.
• cover�surface�corrosion,�onlyrust-through�corrosion,�or�panelsrepaired�under�warranty.
OEM�warranties�generally�do�not�cover�surfacecorrosion�on�frame�rails.
Items�OEM�warranties�may�not�coverinclude:
• cosmetic�or�surface�corrosion�fromstone�chips,�scratches,�hail,�or�acidrain.
• surface�corrosion�on�theunderbody.
• body�panels�repaired�or�refinishedthat�are�not�part�of�a�warrantyrepair.�In�order�to�compensate,some�repair�facilities�may�offertheir�own�warranty.
Vehicle�Maker-Specific�Recommendations
Refer�to�Module�4,�“Activity:�VehicleMaker�Recommendations�Handout”�in
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 64
the�presentation�for�an�exercise�on�vehiclemaker�recommendations.
Refer�to�“Video:�ChryslerRecommendations”�in�the�presentation.This�is�a�video�interview�on�Chrysler'sselection�of�materials�for�corrosionprotection.
Chrysler�300
Among�Chrysler�recommendations�are�severalbody�side�applications�for�weld�bonding,�which�isa�combination�of�using�structural�adhesive�and�spotwelds.
Chrysler�Group�LLC�recommendationsinclude�the�following:
• Do�not�use�weld-throughprimer.�Chrysler�is�alone�in�thisrecommendation.�Chrysler�seesno�benefit�from�weld-through
primer.�These�primers�pollute�theweld�and�also�burn�back�fromthe�weld�zone�causing�corrosionhot�spots.�Adequate�coveragewith�anti-corrosion�compoundprovides�the�highest�level�ofcorrosion�protection�possiblewhen�weld�bonding�cannot�beused.�No�protection�on�the�weldmating�surfaces�is�a�concern,but�the�repair�technician�hasthe�opportunity�during�the�anti-corrosion�compound�applicationto�focus�on�applying�materialsthat�will�eliminate�or�reduce�thecorrosion�concern.
• Apply�structural�adhesive�on�weldbond�areas.�These�adhesives�havecorrosion-inhibiting�properties.
• If�it�is�unknown�whether�theoriginal�application�is�an�adhesiveor�sealer,�use�structural�adhesive.
Chrysler�specifies�to�apply�undercoating�and�anti-corrosion�compound�with�a�spray�applicator�gun.
Chrysler�Group�LLC�recommendationsalso�include�the�following:
• Seal�hem�flanges�on�closurepanels�whether�a�sealer�is
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 65
apparent�or�not.�This�includesseams�disturbed�during�repairsand�on�new�replacement�panels.Either�duplicate�the�existing�beadin�shape�or�size,�or�seal�the�hemflange�in�a�discrete�fashion.�UseMopar�product,�Fusor�129,�or�3M08308.
• Seal�exterior�lap�joints,�visible�ornot.
• Use�a�spray�applicator�gunfor�applying�anti-corrosioncompound.�Coat�inner�cavitiesafter�refinishing,�but�beforeapplying�all�of�the�trim.�Use�thespecific�Mopar�product�number�or3M�Rustfighter.�Apply�two�coatswith�a�minimum�30-minute�drytime�between�coats.
Apply�undercoating�to�wheelhousesand�underbody�areas�involved�in�therepair�process�using�a�spray�applicatorgun.�Use�the�specified�Mopar�product�orequivalent.
Chrysler�collision�repair�information�canbe�found�on�the�TechAuthorityII�website.The�TechAuthorityII�website�is�a�pay�sitefor�service�manual�information,�but�theBody�Repair�Manuals�are�excluded�fromthat�requirement.�Anyone�may�log�in�at�nocharge,�once�they�have�created�a�user�ID,and�access�the�collision�information.
Refer�to�“Video:�Ford�Motor�CompanyRecommendations”�in�the�presentation.This�video�explains�Ford�Motor�Companyrecommendations�for�applying�anti-corrosion�coatings.
Ford�Motor�Company�specifies�PM-24�rust�inhibitorand�PM-25�undercoating.
Ford�Motor�Company�recommendationsinclude�the�following:
• Use�Motorcraft�PM-24�rustinhibitor�for�exposed�finishedsurfaces�or�after�bare�metalrepairs.�PM-24�is�available�for�usewith�a�spray�applicator�gun,�andan�aerosol�for�spot�repairs.
• Use�Motorcraft�PM-25�forundercoating.�PM-25�is�solvent-based�but�does�contain�wax�tokeep�it�flexible�in�cold�weather.
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 66
Apply�the�material�in�light�mistcoats.
• Use�Motorcraft�PM-13�forunderbody�paint�on�trailerhitches,�suspension�arms,�etc.PM-13�was�formerly�the�coatingrecommended�for�all�underbodyareas.
• Use�the�recommended�Motorcraftapplication�equipment,�includingan�applicator�gun�and�wands.�Onewand�has�a�360°�tip�and�another�isshort�with�a�hook-shaped�wand.
Refer�to�“Video:�GM�Recommendations”in�the�presentation.�This�video�explainsGM�recommendations�for�applying�anti-corrosion�coatings.
Chevrolet�Sonic
General�Motors�lists�specific�paint�systems�for�repairsto�their�products,�such�as�this�2011�Chevrolet�Sonic.
General�Motors�Companyrecommendations�include�usingspecific�primers�and�paint�systemslisted�on�their�free�website.�Go�towww.genuinegmparts.com,�accept�theTerms�of�Use,�pull�down�the�“CollisionRepair”�tab�and�choose�“Technical�Info”,then�“Anti-Corrosion�Treatment�andRepair.”�Choose�the�“Paint�Shop”�tab�forrecommended�paint�systems.
Honda�Accord�Crosstour
Honda�/�Acura�recommends�referencing�charts�ontheir�website�for�corrosion�protection�repairs�to�theirproducts�such�as�the�Honda�Accord�Crosstour.
Honda�/�Acura�recommendations�includethe�following:
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 67
• Apply�undercoating�to�a�minimum0.4�mm�thickness,�and�0.5�mm�onwheelhouses�and�the�lower�dash.
• Follow�the�charts�for�each�vehicleon�the�Honda�website,�includingwhere�to�apply�anti-corrosioncompound,�undercoating,�andseam�sealers.
• There�are�no�specific�undercoatingor�anti-corrosion�materialsrecommended.�Follow�thematerial�maker�recommendationsfor�application.
Mitsubishi�Eclipse
Mitsubishi�recommends�brush-on�weld-throughprimer,�but�only�for�spot�welding�on�their�products,such�as�the�Eclipse.
Mitsubishi�recommendations�include�thefollowing:
• Use�brush-on�weld-throughprimer.�Mitsubishi�refers�to�weld-through�primer�as�a�brush-onelectroconductive�spot�sealer.There�are�no�specific�productrecommendations,�only�to�use�abrush-on�type.�It�is�recommendedto�allow�the�primer�to�dry�to�the
touch,�about�30�minutes,�beforespot�welding.
• There�are�no�guidelines�for�usingweld-through�primer�when�GMA(MIG)�welding.
• Undercoating�film�thicknessshould�be�at�least�0.75�mm(.0.03").
Infiniti�M
Nissan�/�Infiniti�wants�technicians�to�apply�aBitumen�wax�after�applying�undercoating�to�vehicles,such�as�the�Infiniti�M.
Nissan�/�Infiniti�recommendations�includethe�following:
• Confine�finish�removal�duringwelding�to�a�minimum.
• There�are�no�specific�productrecommendations�for�anti-corrosion�compound,�though�it�issuggested�to�look�for�one�whichwill�penetrate�after�applicationand�has�a�long�shelf�life.
• Apply�Bitumen�wax�afterundercoating.�Again,�nospecific�recommendations�forundercoating�products,�butselect�one�which�is�rust-resistant,soundproof,�vibration-proof,
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 68
shock-resistant,�adhesive,�anddurable.
Toyota�Tundra
Toyota�/�Lexus�prefers�epoxy�primer�instead�of�self-etching�primer�on�general�areas,�and�epoxy�primerinstead�of�pinchweld�primer�on�stationary�glasspinchwelds.
Toyota /�Lexus�recommendations�includethe�following:
• Apply�epoxy�primer�before�bodyfiller.�One�of�the�reasons�for�thisis�because�of�the�process�used�toapply�a�zinc�coating�on�panels,called�“Excelite.”�This�process�istwo�layers�of�zinc�plus�a�layer�ofiron.�The�iron�coating�is�designedto�help�finish�adhesion.�Epoxyprimer�is�the�only�primer�thatprovides�the�same�protection.
• Fill�scratches�on�a�stationary�glasspinchweld�with�epoxy�primer,not�pinchweld�primer.�Pinchweldprimer�does�not�provide�propercorrosion�protection�on�the�baremetal.
• The�first�choice�for�sectioningjoints�is�epoxy�primer,�not�self-etching�primer.
Audi�TT
When�repairing�Audi�vehicles,�such�as�the�rear�ofthis�TT,�specially�coated�bolts�are�used�for�fasteningaluminum�or�magnesium�to�steel.
Audi�recommendations�include�thefollowing:
• Use�Dacromet-coated�bolts�forfastening�aluminum�or�magnesiumto�steel.�These�bolts�are�one-time-use.
• Non-metallic�fasteners�or�sealersshould�be�non-conductive.
Audi�recommends�this�series�of�coatings�after�repairsto�an�aluminum�panel.
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 69
Audi�has�a�specific�sequence�of�coatingswhen�repairing�aluminum.�This�includesthe�following:
1. Audi�aluminum�body�filler2. One-part�aerosol�primer3. Two-part�aerosol�primer4. Polyester�body�filler5. Two�aerosol�primers�(again)6. Topcoats
BMW�5�Series�Gran�Turismo
BMW�considers�cavity�protection�with�anti-corrosioncompound�the�most�important�step.
BMW�recommendations�include�thefollowing:
• There�are�BMW-specific�partnumbers�for�the�recommendedweld-through�primer,�anti-corrosion�compound�or�cavityprotection,�and�undercoating.One�of�the�recommendedundercoatings�is�waterborne.
• Cavity�protection�is�the�mostimportant�of�all�corrosionprotection�applied�by�the�repairfacility.�Apply�anti-corrosioncompound,�called�“cavity�spray,”
in�cavities�after�refinishing.�Minorcavity�spray�is�aerosol,�and�majorcavity�spray�is�applied�with�a�sprayapplicator�gun.�The�specified�sprayapplicator�gun�also�has�a�BMWpart�number.
BMW�128i
BMW�recommends�removing�the�zinc�coating�whendoing�GMA�(MIG)�welds.
BMW�recommendations�also�include�thefollowing:
• Remove�the�finish�coatings�about30�mm�around�a�weld�seam�orspot,�and�on�the�reverse�side�ofthe�weld�seam�or�spot.�If�not,contaminants�will�enter�the�weldpool�via�the�root�of�the�weld�seam.
• Remove�the�zinc�coating�for�GMA(MIG)�welds,�and�coat�all�metaloverlaps�and�weld�spot�flangeswith�weld-through�primer.
• Remove�the�finish�and�zinccoating�before�brazing.
• Do�not�burn�off�PVCundercoating,�which�wouldgenerate�hydrochloric�acid�andharmful�fumes.�Also,�a�new
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 70
coating�will�not�form�a�satisfactorybond�with�burnt�PVC�material.
BMW�X5�Diesel
BMW�is�among�some�vehicle�makers�that�do�notapply�anti-corrosion�compounds�inside�aluminumcavities,�but�recommend�it�be�applied�after�repairs.
Considerations�for�BMW�aluminumpanels�include:
• new�aluminum�doors,�deck�lids,and�side�panels�are�not�sealedwith�anti-corrosion�compound�orcavity�protection.
• cavities,�seams,�and�folds�formedfrom�new�parts�must�be�treatedwith�anti-corrosion�compoundafter�repairs,�after�refinishing.
Jaguar�XJ
Jaguar�has�a�specific�list�of�recommended�productmakers�for�corrosion�protection�materials�used�ontheir�vehicles,�such�as�the�aluminum-intensive�XJ.
Jaguar�recommendations�include�thefollowing:
• The�service�information�has�a�listof�recommended�product�makersfor�materials�and�applicator�guns.
• There�are�listed�methods�to�avoidgalvanic�corrosion�on�aluminumbodies.
Jaguar�XJ
Jaguar�recommends�priming�internal�areas�beforeapplying�anti-corrosion�compound.
Jaguar�recommendations�also�include�thefollowing:
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 71
• Apply�brush-on�Jaguar-brandweld-through�primer�to�steelmating�flanges�and�allow�it�to�dry.This�recommendation�is�for�spotwelding�only.
• Remove�the�finish�material�andzinc�on�GMA�(MIG)�sectioningjoints�with�a�wire�brush,�not�agrinder,�which�would�weakenthe�structure.�It�is�importantfor�the�weld�quality�that�theinner�area�is�bare�metal.�Zincand�finish�residues�in�the�weldarea�burn�and�cause�seriousporosity�during�welding.�The�sootproduced�prevents�satisfactorycavity�protection.�A�10�mm�widthof�the�underlying�zinc�layer�mustbe�removed�along�the�weld�line.
• Prime�internal�areas�beforeapplying�anti-corrosioncompound.�Treat�all�interiorsurfaces�which�have�beendisturbed�by�repairs,�whether�theywere�treated�with�anti-corrosioncompound�during�productionor�not.�This�includes�all�boxmembers,�cavities,�and�doorinteriors.
Porsche�Panamera
Among�Porsche’s�instructions�is�refinishing�interiorsto�the�exterior�color�before�welding.
Porsche�prefers�“instructions”�rather�than“recommendations.”�Those�instructionsinclude�the�following:
• Apply�weld-through�primer,called�“zinc�dust�paint”�in�theservice�information,�on�the�matingflanges.�There�is�no�specific�brand.
• Apply�two-part�primer�to�baremetal�areas.
• Refinish�interiors�to�the�exteriorcolor�before�welding.
• Apply�undercoating�in�differentthicknesses�by�area,�identifiedin�the�service�information.�Thebrands�of�specific�undercoatingand�chip-resistant�coatingrecommended�are�listed�in�theservice�information.�The�“gravelguard”�undercoating�is�the�samematerial�as�is�used�for�some�chip-resistant�coating�applications.Exterior�underbody�surfacesshould�have�undercoating�installedonly�to�primed�surfaces.
Module�4�-�Vehicle�Maker�RecommendationsTextbook
Corrosion�Protection 72
Volkswagen�Touareg�Hybrid
Specific�undercoating�recommended�for�Volkswagenvehicles�includes�a�wax-based�product.
Volkswagen�recommendations�include�thefollowing:
• Apply�VW�weld-through�primer,an�aerosol,�to�both�mating�flanges.
• Use�zinc�packing�for�hinges,�etc.Zinc�packing�is�supplied�in�bagsand�is�used�for�doors,�the�tailgate,and�hood�hinges.
• Apply�anti-corrosion�compound�asdirected,�which�includes�a�brownsealant�and�a�preservation�wax.
• Apply�undercoating�as�directed.The�specified�undercoatingmaterial�includes�long�term,�blackstone�impact,�and�a�wax-basedproduct.
Volvo�classifies�the�different�seams�for�a�better�guideon�which�seam�sealer�to�use�during�repair.
Volvo�recommendations�include�thefollowing:
• Apply�brush-on�Volvo-brand�weld-through�primer�on�weld�matingsurfaces.
• Use�a�special�spray�gun�for�anti-corrosion�compound�or�cavitywax.
• Seams�are�classified�as�A,�B,�andD.�“A”�class�seams�are�most�visibleand�include�outer�panels�such�asthe�roof.�“B”�class�seams�are�lessvisible�and�usually�apply�to�doorpanel�seams.�“D”�class�seams�arenot�visible,�where�appearance�isnot�a�factor,�but�must�be�liberallyapplied�for�a�good�seam.
Volvo�has�their�own�part�numbers�andrecommendations�for�seam�sealers,including�their�own�spray�sealer,�stonechip�protection�with�a�Volvo�sprayapplicator�gun,�and�aerosol�rustproofingagents.
Module�Wrap-Up
Topics�discussed�in�this�moduleincluded:
• what�is�covered�and�not�coveredin�OEM�warranties.
• corrosion�protectionrecommendations�from�differentvehicle�makers.