03 Steel Preparation_grade1

7/28/2019 03 Steel Preparation_grade1

1/27

Paint School1

Pre-blasting preparation


2/27

Paint School2

Most coating failures

result from poor or inadequate:

Steel preparation

Cleaning

Surface preparation

Application Access

Ventilation

Coating selection

Inspection and control

Premature exposure

(Exposed too soon)


3/27

Paint School3

Investigation by a Guarantee

Insurance company has shown:

95 % of all coating failures result from

Poor surface preparation

Poor application

85 % of all failures appear within 1-2 years

This fits in well with our own experience


4/27

Paint School4

Rounding or smoothing of: Sharp edges

Corners

Welds

Grinding of:

Laminations

Flame cut edges

Weld spatter


involves the following activities

Notches minimum diameter: 30 mm

Inspected and approved before cleaning

See ISO 8501 Visual assessment of surface cleanliness


5/27

Paint School5

A

B

Gas cut edgeA. Remove by grinder or disc sander.

B. Rolled steel sections normally have

round edges. Therefore can beleft untreated.

A. Remove visible spatter before grit-blasting with grinder or chipping

hammer.

B. For spatter not readily removed,

remove using grinder/disc.

Sharpedge

Weldspatter

A

B

Steel preparation

Edges and weld spatters


6/27

Paint School6

Coating applied to a square-cut section


Rounding sharp edges

Reduced coating thickness at

sharp edges due to tensioncreated during drying / curing

Coating

Sharp edge

Rounded edgeEven coating

thickness

Steel


7/27

Paint School7

Cross section of

painted steel with a sharp edge

Paint applied with spray

Forms inferior coating thickness around the edge

Cd-4932-21

Steel

Paint


8/27

Paint School8

Cross section of painted steel

construction with well rounded edge

Paint applied by spray

Forms even thickness around the edge

Cd-4932-20

Steel

Paint


9/27

Paint School9

Grinding of sharp edges, welds etc.

Disc sander and disc grinder

Sander for removing mill

scale, paint and rust

Cd-4932-03

Grinder for heavy grinding,

such as edges and weld beads


10/27

Paint School10

Steel support prior to

pre-blasting preparation

Sharp edges Rust grade: A to B according to ISO 8501

Cd-4930-46


11/27

Paint School11

Edge rounded with disc grinder

A well rounded edge will ensure a sufficient paint film

over the entire construction

Cd-4932-12


12/27

Paint School12

Steel support after

blast-cleaning to Sa 2

The sharp edges have been rounded prior to blast-cleaning:

Good !

Cd-4930-48


13/27

Paint School13

Weld with pinhole.

Visible through the paint system

Will lead to initiation of corrosion Remedial actions: Remove the paint, re-weld and grind. Apply

paint

Cd-4930-42

NOTE:Such defects may

be difficult to find

during inspection


14/27

Paint School14

Early corrosion on sharp edge

and spot welds

Paint has newly been applied

Exposed to wind and weather for approximately 2 weeks

Cd-4930-78


15/27

Paint School15

Insufficient pre-blasting

preparation

Notch

Power tooling has been carried out

Sharp edge not grinded

Cd-4932-16


16/27

Paint School16

Severe corrosion due to a

combination of several effects

Sharp edges

Rough welds (not grinded)

Missing stripe coating

Cd-4930-71


17/27

Paint School17

Severe corrosion due to a

combination of several effects

Cd-4930-72

Sharp edges

Rough welds (not grinded)

Missing stripe coating


18/27

Paint School18

Small weld spatters

Even only one small weld spatter may be sufficient to initiatecorrosion which with time may lead to severe problems

Cd-4930-45NOTE:

Small failures

like this are

difficult to find


19/27

Paint School19

Remaining weld beads after removal of

supports welded on to the structure

Prior to pre-treatment these must be grinded away to

form an acceptable substrate for the paint system

Cd-4932-04


20/27

Paint School20

Remove using grinder

Undercuts exceeding classification rulingshould be repaired by welding and grinding.

Sharp profile peaks to be smoothed usinggrinder

Lamination

Undercut

Manual weld bead


Laminations, undercuts, welding seams


21/27

Paint School21

Cd-4930-39

Unacceptable weld.

Too rough and full of pinholes / pores

Weld spatters close to weld

Rewelding and grinding must be carried out

prior to reblasting and painting


22/27

Paint School22

Paint on a very poor weld. Pinholes and

holidays visible after second stripe coating

Neither rewelding nor grinding have been

carried out prior to application

Remedial Actions: Reblasting, rewelding,

grinding and blast -cleaning: COSTLY

Cd-4930-41


23/27

Paint School23

Paint applied on a very poor weld.

Pinholes and holidays visible after application

Neither rewelding nor grinding have beencarried out prior to application

Remedial Actions: Reblasting, rewelding,

grinding and blast -cleaning: COSTLY

Cd-4930-40


24/27

Paint School24

Not recommended solution for exposure to severe /

aggressive environments

Spot welding leads to crevices

which are susceptible to corrosion

Cd-4930-36


25/27

Paint School25

Spot welds after painting

Paint is unable to fill

gap between the parts

welded together

These area may be

susceptible to

corrosion

Not recommended for

exposure to severe /

aggressiveenvironments

Cd-4930-37


26/27

Paint School26

Sharp edge an spot welds.

Early corrosion attack

Construction newly

painted

Exposed to humid

atmosphere

Corrosion initiates

after a short period of

time on weak areas:

Sharp edges, crevices

and spot welds

Cd-4930-38


27/27

Paint School


Grinding a small construction

Mark areas where

grinding are required

Remove weld spatters

Grind the welds

Grind the notches

Important to carry out the

grinding to improve the

life time of the paintsystem

Pre-treatment: Grind_spatters1

Documents

03 Steel Preparation_grade1