The Effect of Four Commercially Available

Steel Decontamination Processes

on the Performance of External Coatings

Michael Melancon Chevron M&EE, Richmond, CA, USA

Amal Al-Borno, Ph.D. Charter Coating Service (2000) Ltd., No. 6, 4604 13th Street NE,

Calgary, AB, T2E, Canada

CO-AUTHORS

Paul Hunter

Chevron M&EE, Richmond, CA, USA

Steve Hourcade

Chevron North America E&P, Northpark Boulevard, Covington, LA, USA

Tomasz Liskiewicz, Sherry Rao Bassem Salamah, Shailesh Dhoke,

Julius Cortes and Xianyi Chen

Charter Coating Service (2000) Ltd., Calgary, AB, Canada

Coating systems used for corrosion protection in external service

frequently have to perform under severely corrosive environments.

In such instances, it is important that these coatings must be able to

withstand:

Effect of weather

Ultraviolet light

Industrial/marine atmospheres

External Tank Linings

Even the best coating will fail if it is applied to a contaminated surface

ISO 8502 Standard says: The behavior of protective coating

systems is affected mainly by the condition of the

substrate immediately before the coating system is

applied

Behavior of protective coating systems is controlled by:

Rust and mill scale

Surface profile

Debris contamination

Soluble salts

Problem of Surface Contamination

Most common salts in the industrial environment:

chlorides (Cl-),

sulphates (SO42-)

nitrates (NO3-)

Problem of soluble salts became more significant over recent years

Driven by environmental legislation replacing lead-bearing paints

The presence of soluble salts on the metallic substrate will lead to

osmotic coating blistering

Soluble Salts

Soluble salts

Interfacial water

Most common salts in the industrial environment:

chlorides (Cl-),

sulphates (SO42-)

nitrates (NO3-)

Problem of soluble salts became more significant over recent years

Driven by environmental legislation replacing lead-bearing paints

The presence of soluble salts on the metallic substrate will lead to

osmotic coating blistering

Soluble Salts

Concentrated salt solution

Most common salts in the industrial environment:

chlorides (Cl-),

sulphates (SO42-)

nitrates (NO3-)

Problem of soluble salts became more significant over recent years

Driven by environmental legislation replacing lead-bearing paints

The presence of soluble salts on the metallic substrate will lead to

osmotic coating blistering

Soluble Salts

Water drawn in

by osmotic pressure

Most common salts in the industrial environment:

chlorides (Cl-),

sulphates (SO42-)

nitrates (NO3-)

Problem of soluble salts became more significant over recent years

Driven by environmental legislation replacing lead-bearing paints

The presence of soluble salts on the metallic substrate will lead to

osmotic coating blistering

Soluble Salts

Soluble salts

Interfacial water

General trend very low salt concentration values by coating

manufacturers and standard issuing organizations

BUT

These low values seem to be very conservative as they must

represent different coating systems and different operational

conditions

Benefits of applying surface cleaning procedures

should be assessed on an individual

Soluble Salts

Scope of this project

Maximum Cl- level advised by Chevron in this project: 5g/cm2

Project Motivation

Chevron’s offshore facilities have been addressing

challenges of maintenance coating issues for a

number of years

The service life of previous maintenance coating

systems has not met expectations

Project Objective

To determine the effectiveness of three

commonly used surface pre-cleaning methods

along with a post blast chemical cleaning

method.

It was anticipated that the results of this study

will assist Chevron in selecting cleaning

methods and coatings in order to improve the

service life of external coating systems

Project Objective

Coating Systems

Coating Suppliers

Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5

Coating

System 1 7-10 years

Coating

System 2 15-20 years

Coating

System 5 7-10 years

Coating

System 3 7-10 years

Coating

System 4 15-20 years

Coating

System 6 15-20 years

Coating

System 7 7-10 years

Coating

System 8 15-20 years

Coating

System 9

Coating

System 10

Approved suppliers

New suppliers

Coating Systems for

Gulf of Mexico Application

Supplier Coating system Coating Type

1 CS1 12-15 mils

7-10 year system

Epoxy Mastic (aluminum-pigmented high-solids mastic)

Cycloaliphatic Amine Epoxy- Top Coat

1

CS2 14-18 mils

7-10 year system

Polymeric Epoxy Amine

Epoxy Mastic – Top Coat

Cycloaliphatic Amine Epoxy – Top Coat

1 CS3 16-24 mils

15-20 year system

Solvent Based Organic Zinc-Rich Epoxy

Epoxy Mastic

Epoxy Mastic

Modified Siloxane Hybrid- Top Coat

1 CS4 18-26 mils

15-20 year system

Epoxy Mastic

Epoxy Mastic

Epoxy Mastic

Modified Siloxane Hybrid – Top Coat

2 CS5 16-20 mils

7-10 year system

Surface Tolerant Epoxy

Modified Epoxy – Top Coat

2 CS6 12-17 mils

15-20 year system

Aluminum Pure Epoxy

Aluminum Pure Epoxy

Acrylic Polysiloxane- To Coat

3 CS7 12-15 mils

7-10 year system High Solids Glass Flake Epoxy

Polyamide Epoxy (containing Zn phosphate)- Top Coat 3

CS8 25-27 mils

15-20 year system

4 CS9 6-9 mils Zinc Silicate

Siloxane Epoxy – Top Coat

5 CS10 22 mils Epoxy Primer/Sealer

Elastomeric Pure Polyurea – Top Coat

Cycloaliphatic Amine Epoxy

20%

High Solids Glass Flake

Epoxy20%

Modified Siloxane Hybrid

20%Modified Epoxy 10%

Acrylic Polysiloxane

10%

Siloxane Epoxy10%

Elastomeric Pure Polyurea

10%

Coating Systems- Top Coat

Epoxy Mastic: Aluminum-pigmented high-solids

mastic20%

Polymeric Epoxy

Amine-Aluminum-pigmented high-solids

mastic10%

Organic Zinc-Rich Epoxy-Aluminum-pigmented high-solids

mastic

10%

Epoxy, Surface Tolerant Epoxy

20%

Polyamide Epoxy-contain Zn phosphate

20%

Zinc Silicate10%

Aluminium Pure Epoxy

10%

Coating Systems-Mid and base Coat

Coating Systems

• Four cleaning methods: – Cleaning Method A :

Industry standard pressure wash

– Cleaning Method B: Pressure wash with fresh 25% aqueous

cleaning solution used by Chevron

– Cleaning Method C: New chemical treatment

– Cleaning Method D: Simulates Chevron offshore

maintenance procedures

when surface blasting is not carried out

Solvent

Clean, Sweep

blast and

contaminated

Solvent Clean, Blast to

SSPC-SP 10 prior to

contamination

Cleaning Methods

To simulate offshore chloride contaminations:

Panels were exposed to a salt fog atmosphere in a salt spray

cabinet conducted as per ASTM B117-11

The exposure time required to achieve a contamination level of

300 Cl- (µg/cm2) was 48 hours

Heavly corroded substrates which showed general and localized

corrosion attack

FIRST STEP: Surface Contamination

To simulate offshore chloride contaminations:

Panels were exposed to a salt fog atmosphere in a salt spray

cabinet conducted as per ASTM B117-11

The exposure time required to achieve a contamination level of

300 Cl- (µg/cm2) was 48 hours

Heavly corroded substrates which showed general and localized

corrosion attack

FIRST STEP: Surface Contamination

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Panel After Contamination

Cleaning Method A

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Panels After Fourth Wash

Cleaning Method A

Blast Cleaning

NACE 2 / SSPC-SP 10

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Low Pressure Wash

3000 psi, fresh tap water

2 minutes

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Panels After Blasting

Cleaning Method A

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Panel After Contamination

Cleaning Method B

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Panels After Third Wash

Cleaning Method B

Blast Cleaning

NACE 2 / SSPC-SP 10

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Low Pressure Wash

3000 psi, 25% cleaning solution

(1 minute) followed by fresh tap

water (1 minute)

Panels After Blasting

Cleaning Method B

Solvent Clean SP 1

Commercial blast to SP6

Contaminate Surface Using Salt Fog

48 hours

Panel After Contamination

Cleaning Method C

Blast Cleaning

NACE 2 / SSPC-SP 10

Solvent Clean SP 1

Commercial blast to SP6

Contaminate Surface Using Salt Fog

48 hours

Panels After Blasting

Cleaning Method C

Blast Cleaning

NACE 2 / SSPC-SP 10

Chemical Treatment

commercial cleaning solution,

45 minutes

Solvent Clean SP 1

Commercial blast to SP6

Contaminate Surface Using Salt Fog

48 hours

Panels During Chemical Treatment

Cleaning Method C

Blast Cleaning

NACE 2 / SSPC-SP 10

Chemical Treatment

commercial cleaning solution,

45 minutes

Washing

proprietary wash solution

Solvent Clean SP 1

Commercial blast to SP6

Contaminate Surface Using Salt Fog

48 hours

Panels After Wash

Cleaning Method C

Panel After Contamination

Blast Cleaning

NACE 2 / SSPC-SP 10

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Cleaning Method D

Panels After UHP Wash

Ultra-high Pressure

Water Jetting

36000 psi, fresh tap water

2 minutes

Blast Cleaning

NACE 2 / SSPC-SP 10

Contaminate Surface Using Salt Fog

48 hours

Solvent Clean SP 1

Commercial blast to SP6

Cleaning Method D

Two methods for measuring the chloride contamination level were used in

this study:

1. Laboratory Ion Chromatography

Dionex DX-120 Ion Chromatography system

2. Field method

commercial chloride ion detection kit

• Chloride analysis was conducted using a laboratory extraction process

conducted according to Mayne approach

Chloride Analysis

Maximum Cl- level advised by Chevron in this project: 5g/cm2

Two methods for measuring the chloride contamination level were used in

this study:

1. Laboratory Ion Chromatography

Dionex DX-120 Ion Chromatography system

2. Field method

commercial chloride ion detection kit

• Chloride analysis was conducted using a laboratory extraction process

conducted according to Mayne approach

Cleaning Method

Laboratory Method Ion Chromatography

Cl- (µg/cm2)

Field Method Cl- (µg/cm2)

Cleaning Method A 0.8 - 2.33 0

Cleaning Method B 1.4 - 1.9 0

Cleaning Method C

1.4 - 2.13 0

Cleaning Method D 1.2 - 2.7 0

Chloride Analysis

Maximum Cl- level advised by Chevron in this project: 5g/cm2

Before cleaning

• Highly contaminated steel

surface with many deposit

patches (1.88% wt. chloride

contamination by EDX)

After cleaning

• Highly deformed, rough surface

resulting from blasting

• No significant contamination

deposits observed by SEM

• However EDX showed traces of

chloride

Before Cleaning

Cleaning Method A

Cleaning Method B

Cleaning Method C

Cleaning Method D

oxides

SEM/EDX Analysis

In order to achieve conformity of application conditions, all the

coatings were applied at the same location by the same applicator.

The applications were observed by a Charter Coating inspector and

witnessed by a representative of each coating supplier.

Coating Application

Ultra-high Pressure Cleaning

Ultra-high Pressure Cleaning

Tests performed included:

1. Adhesion

Pull-off - ASTM D4541-09

X-scribe - ASTM D6677

2. Cross-section porosity - CSA Z245.20

3. EIS - ISO 16773-2: 2007

4. Cycling testing - ASTM D5894

Laboratory Testing

Duration: 1008 hours (6 weeks) in total

Post-test evaluation:

Blistering

Checking rating

Color change

Gloss

Chalking

Rusting

Undercreep

Cycling Test - ASTM D5894

Duration: 1008 hours (6 weeks) in total

Post-test evaluation:

Blistering

Checking rating

Color change

Gloss

Chalking

Rusting

Undercreep

Fluorescent

UV/condensation

1 week (168h) Cycle

Cyclic Salt Fog/Dry Exposure

1 week (168h) Cycle

4h UV Light at 60oC

4h Condensation at 50oC

1h Fog at Ambient

Temperature

1h Dry-Off at 35oC

Salt Solution: 5% NaCl

Cycling Test - ASTM D5894

No adhesive failure at the coating system/substrate interface has

been reported for any coating system

The cleaning methods indicate good coating application process

leading to high interface strength.

The pull-off strength of the coating system was found to be a factor of

the coating type and not the cleaning method.

Sample results – Coating System 5:

Cleaning

Method A

Cleaning

Method B

Cleaning

Method C Cleaning

Method D

Pull-off Adhesion - ASTM D4541-09

0

500

1000

1500

2000

2500

3000

3500

A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D

CS1 CS2 CS3 CS4 CS5 CS6 CS7 CS8 CS9 CS10

Pu

ll-O

ff P

si

Coating System"CS1-10 and Cleaning Methods A-D"

Pull-off Adhesion (psi)

Pull-off Adhesion Test Results

All coating systems showed no sign of any adhesive or brittle

breakaway from the substrate indicating excellent coating to substrate

adhesion.

For the same type of coating, the variation in the substrate cleaning

method did not affect the coating adhesion.

Sample results – Coating System 9:

Cleaning

Method A

Cleaning

Method B

Cleaning

Method C Cleaning

Method D

X-cut Adhesion - ASTM D6677

According to CAN/CSA Z245.20 - 10, Clause 12.10, cross-section

porosity is ranked between 1 and 5, with 1 indicating the lowest and 5

the highest porosity.

For all analyzed samples, both cross-section porosity and interface

porosity were ranked between 1 and 2 indicating very low porosity.

Sample results – Coating System 3:

Cross-section Porosity - CSA Z245.20, section 12.10

EIS - ISO 16773-2: 2007

6

6.5

7

7.5

8

8.5

9

9.5

10

10.5

11

A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D

CS1 CS2 CS3 CS4 CS5 CS6 CS7 CS8 CS9 CS10

Lo

g Z

(O

hm

s/c

m2

Coating System"CS1-10 and Cleaning Methods A-D"

EIS Log Z (Ohms/cm2)

Pass

Cycling Test: Results

Cycling Test: Results

Cycling Test: Results

0

5

10

15

20

25

30

35

40

A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D

CS1 CS2 CS3 CS4 CS5 CS6 CS7 CS8 CS9 CS10

DFT

mils

Coating Systems "CS1-10 and Cleaning Methods A-D"

DFT mils Before and after the Cycling Test

DFT (mils) Pre-test DFT (mils) Post-test

Cycling Test: Results

0

1

2

3

4

5

6

A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D

CS1 CS2 CS3 CS4 CS5 CS6 CS7 CS8 CS9 CS10

Un

de

rcre

ep m

m

Coating System"CS1-10 and Cleaning Methods A-D"

Undercreep (mm)

Cycling Test: Results

CS1

Epoxy

Mastic

(Aluminum-

pigmented

high-solids

mastic

Cycloaliphati

c Amine

Epoxy

CS2

Polymeric Epoxy

Amine/ Epoxy

Mastic/ Cycloaliphatic Amine

Epoxy

CS3

Solvent Based Organic Zinc-Rich Epoxy/2layers of Epoxy Mastic/ Modified Siloxane Hybrid

CS4

3 Layers of Epoxy Mastic/

Modified Siloxane Hybrid

CS5

Surface Tolerant Epoxy / Modified Epoxy

CS6

2Layers of Aluminum Pure Epoxy/ Acrylic Polysiloxane

CS7

Polyamide Epoxy (contain Zn phosphate)/ High Solids Glass Flake Epoxy

CS8

Polyamide Epoxy (contain Zn phosphate)/ High Solids Glass Flake Epoxy

CS9

Zinc Silicate/ Siloxane Epoxy

CS10

10

Epoxy Primer/Sealer/ Elastomeric Pure Polyurea

Cycling Test: Checking

Yes

CS5

Surface

Tolerant

Epoxy /

Modified

Epoxy

CS7

Polyamide

Epoxy

(contain Zn

phosphate)

/ High

Solids

Glass Flake

Epoxy

CS8

Polyamide

Epoxy

(contain Zn

phosphate)

/ High

Solids

Glass Flake

Epoxy

CS10

Epoxy

Primer /

Sealer /

Elastomeric

Pure

Polyurea

No

CS1

Epoxy

Mastic

(Aluminum-

pigmented

high-solids

Mastic /

Cycloali-

phatic

Amine

Epoxy

CS2

Polymeric

Epoxy

Amine /

Epoxy

Mastic /

Cycloali-

phatic

Amine

Epoxy

CS3

Solvent

Based

Organic

Zinc-Rich

Epoxy /

2 layers

Epoxy

Mastic/

Modified

Siloxane

Hybrid

CS4

3 Layers of

Epoxy

Mastic /

Modified

Siloxane

Hybrid

CS6

2 Layers of

Aluminum

Pure

Epoxy /

Acrylic

Polysilo-

xane

CS9

Zinc Silicate

/ Siloxane

Epoxy

Summary: Supplier 1

Coating System Cleaning Methods

Cycling Test Results

Color

Change Checking

Undercreep

(mm) rating

CS1

Cleaning Method A Slight None 0.4 9

Cleaning Method B Slight None 0.1 9

Cleaning Method C Slight None 0.5 9

CS2 Cleaning Method D Slight None 3.1 5

CS3

Cleaning Method A None None 0 10

Cleaning Method B None None 0 10

Cleaning Method C None None 0 10

CS4 Cleaning Method D None None 1.8 7

For all four coating systems no significant change in DFT, no blistering, no rusting,

no cracking and no checking

Slight change in color and loss of gloss for CS1 and CS2

CS2 and CS4 showed tendency to undercreep

Results indicate that effective surface cleaning and blasting is required for better

coating utilizing epoxy mastic as a first coat

Loss of gloss is due to use of the modified siloxane hybrid as a top coat

Summary: Supplier 2

Coating System Cleaning Methods

Cycling Test Results

Color

Change Checking

Undercreep

(mm) rating

CS5

Cleaning Method A Medium Yes 1.7 7

Cleaning Method B Medium Yes 2.5 6

Cleaning Method C Medium Yes 1.6 7

Cleaning Method D Medium Yes 4.6 5

CS6

Cleaning Method A None None 2.3 6

Cleaning Method B None None 2.4 6

Cleaning Method C None None 1.1 7

Cleaning Method D None None 3.3 5

Similar effect of cleaning on coating performance with no change in DFT, no

blistering, no rusting, no cracking, medium change in color and loss of gloss

Checking was observed for CS5

Undercreep observed in all samples but UHP water jetting (Method D) showed

lower resistance to undercreep

This indicates effective surface cleaning and blasting is required to improve coating

performance with regard to undercreep

Summary: Supplier 3

Coating System Cleaning Methods

Cycling Test Results

Color

Change Checking

Undercreep

(mm) rating

CS7

Cleaning Method A Slight Yes 2.4 6

Cleaning Method B Slight Yes 1.5 7

Cleaning Method C Slight Yes 1.7 7

Cleaning Method D Slight Yes 2.6 6

CS8

Cleaning Method A Slight Yes 1.5 7

Cleaning Method B Slight Yes 2.3 6

Cleaning Method C Slight Yes 2.6 6

Cleaning Method D Slight Yes 4.8 5

The same coatings but CS8 was applied at a higher DFT (24-25 mils) while CS7 at

14 mils

Steel substrate cleaned by UHP water jetting (Method D) showed slightly lower

resistance to undercreep

Similar performance: tendency to undercreep but no change in DFT, no blistering,

no rusting, no cracking, slight change in color, loss of gloss and checking

Summary: Supplier 4

Coating System Cleaning Methods

Cycling Test Results

Color

Change Checking

Undercreep

(mm) rating

CS9

Cleaning Method A None None 0.5 9

Cleaning Method B None None 0.6 8

Cleaning Method C None None 0.8 8

Cleaning Method D None None 0.4 9

Similar effect of cleaning methods on the coating performance from cycling test

No change in DFT, no blistering, no rusting and no cracking, no change in color,

no loss of gloss

Very slight tendency to undercreep (≤ 0.8 mm)

The only coating which has surface tolerant properties for tarnished substrate

The inorganic zinc primer has a chemical bond in additional to a physical bond

between the coating and the steel

Summary: Supplier 5

Coating System Cleaning Methods

Cycling Test Results

Color

Change Checking

Undercreep

(mm) rating

CS10

Cleaning Method A None Yes 1.6 7

Cleaning Method B None Yes 0.9 8

Cleaning Method C None Yes 0.9 8

Cleaning Method D None Yes 1.2 7

All cleaning methods had similar effects on the coating performance

No change in DFT, no blistering, no rusting, no cracking and no change in color

Checking and some loss of gloss were noted for all test samples

Some tendency to undercreep (0.9 - 1.6 mm)

Conclusions

Low salt levels for all methods but UHP wash with no blast before or after

the water jetting resulted in a slightly tarnished substrate due to oxides

formation on steel surface

Differences in gloss change and degree of checking between coatings

which are surface phenomena and formulation related reactions

The only significant difference in coatings performance observed for

undercreep

Most coatings applied after UHP wash showed tendency to undercreep

indicating coating systems sensitivity to substrate preparation

The chemical treatment included in this study (Cleaning Method C), did

not show any significant positive or negative effect on the performance of

the applied coatings

ACKNOWLEDGMENT

The authors would like to thank Chevron

Energy Technology Company in conjunction

with Chevron Gulf of Mexico Business Unit

for their finical and technical support of this work