self-healing coatings for improved corrosion resistance ... · self-healing coatings for improved...

Subramanyam ‘Kasi’ Kasisomayajula

Research and Development ManagerSeptember 10th, 2019

Self-Healing Coatings for Improved Corrosion

Resistance and Adhesion Maintenance

Outline

Protective Coatings for Corrosion Control

Microencapsulated Healing Agents with Various Chemistries

Zinc-Based Sacrificial Protection

Performance Testing via Salt Fog Exposure

- Evaluation of One Coat Systems

- Evaluation of Two Coat Systems

Key Takeaways

Failure in Protective Coatings

0

-81

Fre

e E

ne

rgy C

ha

nge

(Δ

G°

, k-c

al/m

ole

)

Uncoated

Steel

Protective Coating

Coated Steel

Lifetime of Protective Coating

Effective lifetime of coating is limited by

environmental factors and damage

FeOOH line

Without the coating the metal quickly oxidizes to form an oxide with inferior

mechanical properties

Protective coating lengthens lifetime of substrate and lifetime extension depends on

coatings physical and chemical properties

Damage to the coating will compromise its protective capabilities and hasten

degradation of substrate

COST: Annual global cost of corrosion estimated to be US$2.5 trillion (3.4% of

global GDP)*

Adapted from Paint and Coatings Applications and Corrosion Resistance, Schweitzer, P.A.

*http://impact.nace.org/economic-impact.aspx

Improvement in Protective Coatings

Without the coating the metal quickly oxidizes to form an oxide with inferior

mechanical properties

Protective coating lengthens lifetime of substrate and lifetime extension depends on

coatings physical and chemical properties

Damage to the coating will compromise its protective capabilities and hasten

degradation of substrate

COST SAVINGS: Self-healing functionality minimizes impairment of protective

capabilities that occur after damage leading to cost savings

0

-81

Fre

e E

ne

rgy C

ha

nge

(Δ

G°

, k-c

al/m

ole

)

Uncoated

Steel

Protective Coating

Coated Steel

Lifetime of Protective CoatingLifetime Extension due to

Self-Healing Functionality

Protective Coating

Coated Steel

Extension achieved by maintaining more

robust protection after the coating is damaged

Effective lifetime of coating is limited by

environmental factors and damage

FeOOH line

Adapted from Paint and Coatings Applications and Corrosion Resistance, Schweitzer, P.A.

Introduction to Self-Healing Coatings

Traditional Coatings

Used for protective and/or decorative purposes

Functional Coatings

Additional functionality (best described as functional

if functionality is static)

Superhydrophobic, antifouling, intumescent, etc.

Ghosh, 2006 (Editor: Functional Coatings, Wiley)

Smart Coatings

Additional dynamic functionality

Noticeable/predictable response to trigger

mechanism

Challener, 2006 (JPCL/Coatings Tech)

Self-Healing Coatings

Damage triggers protective and/or aesthetic recovery

Non-Autonomic: Healing requires energy from

external source

Autonomic: healing activated by damage, external

intervention not required

TRADITIONAL COATING

FUNCTIONAL COATING

SMART COATING

Healing agent released

to site of damage

Healing agent polymerizes

and heals damageMicrocapsules ruptured

by damage

Self-Healing Microcapsules

Superhydrophobic Surfaces

Corrosion Protection

Cho et al., Adv. Mater. 2009, 21, 645–649

-5

0

5

10

15

20

0 5 10 15 20 25 30

Self-Healing Coatings: Maintenance of Adhesion after Damage

Ad

he

sio

n L

oss (

mm

)

Systems and Chemistries Evaluated

Average Control

Performance

(9.1 mm, rating 3)

Average Self-Healing

Performance

(2.1 mm, rating 7)

130%

Rating

Improvement

Multi-Coat Epoxy Powder

Primer-Based Systems

Multi-Coat Epoxy Zinc

Primer-Based Systems

Single Coat Zinc

Primers

Epoxy Primer-

Based Systems

Polyurethane

DTM

Alkyd Maintenance

Coating

Textured Polyester

Powder Coating

Standard Commercially

Available CoatingStandard Commercially

Available Coating with Self-Healing Additive

Data Mark Size is Proportional to Exposure

Time (Largest Represents 2,500 h)

Outline


Microencapsulated Healing Agents with Various Chemistries





Key Takeaways

Microencapsulated Healing Agents

CAPSULE CORE TECHNOLOGY EXAMPLES OF END-USE APPLICATIONS

Dual Capsule System

Reactive Silicone Polymers with Ability to

Cure Under Water

- Heavy Industrial Protective Coatings

- Maintenance and New Construction

- Fatigue Resistant Adhesives

Single Capsule System

Solvent-Promoted Cure of Epoxy Resin

- Light to Heavy Duty Protective Coatings

- Powder Coatings

- Adhesives and Structural Composites

Single Capsule System

Oxygen-Initiated Cross-Linking of

Functionalized Alkyd Resins

- Industrial Maintenance Coatings

- Protective Wood and Concrete Coatings

- Automotive Undercoatings

Outline


Commercialized Microencapsulated Healing Agents





Key Takeaways


High content of metallic zinc particles form interconnected network

throughout the coating Pigment Volume Concentration (PVC) > Critical Pigment Volume Concentration

(CPVC)

Usually above 60% by volume in solvent-based organic zinc-rich coatings

Reference

ElectrodeCounter

Electrode

Working

Electrode

Electrochemical Test Set-up

0

1

2

3

4

5

6

7

8

9

10

0 50 100 150 200 250

Imp

ed

an

ce (

log

|Z|@

0.1

Hz)

Time of Exposure (Hours)

Control

Unscribed Coating

Salt Fog Exposure (Hours)

1.5

2

2.5

3

3.5

4

4.5

0 50 100 150 200 250

Imp

ed

an

ce (

log

|Z|@

0.1

Hz)

Time of Exposure (Hours)

Control

Scribed Coating


Impedance drop after exposure to salt spray for both

unscribed and scribed coatings indicates salt solution

penetration into pores causing decrease in impedance

Formation of zinc

corrosion products

increases impedance

Exposure started after

coating was scribed

Improving Zinc-Based Protection

Corresponding Electrochemical Data

Systems Evaluated

Control System

Substrate: Cold Rolled Steel (CRS)

Matrix: Epoxy-Based Zinc-Rich Primer

System Incorporating Self-Healing Additive

Substrate: Cold Rolled Steel

(CRS)

Microencapsulated

Epoxy-Based Healing Agent


Release of healing agent

restricts salt solution

uptake at damage site

Scribed Coating

2

2.5

3

3.5

4

4.5

0 100 200

Imp

ed

an

ce

(lo

g|Z

| 0.1

Hz)

Control Self-healing


0

2

4

6

8

10

0 100 200

Imp

ed

an

ce

(lo

g|Z

| 0.1

Hz)

Control Self-healing

Unscribed Coating

Similar impedance indicating

minimal effect of microcapsules

when coating is NOT damaged


Lower cathodic current

(lowering of electrolyte

penetration)

Lower anodic current

corresponds to slower

oxidation of zinc

Scribed Coating

(CR = 2.2 μA/cm2)

(CR = 0.55 μA/cm2)

-1.05

-1

-0.95

-0.9

-0.85

-0.8

-0.75

-4.2 -3.2 -2.2 -1.2 -0.2

Po

ten

tia

l (E

we

/V)

Current (log(|<I>/mA|))

Control

Self-healing

Outline







Key Takeaways

Performance TestingStatic (Standard) Exposure

Used for standard benchmarking studies (most common approach)

Panels are scribed using a 500 micron scribe tool, followed by exposure to ASTM B117 conditions

for a specified duration.

Panels are scraped to remove loose/disbonded material around the scribe and the width of the

disbonded area measured and recorded.

Dynamic Exposure

Simulates more aggressive conditions such as repeated assault to a damaged area during

transportation, installation, or service.

Panels are scribed using a 500 micron scribe tool, followed by exposure to ASTM B117 conditions

for a specified total duration.

Panels are scraped every 250 h to remove loose/disbonded material around the scribe and the

width of the disbonded area measured and recorded.

Scribe

Panels

End Exposure

Scrape Test

Start Salt Fog

Exposure

24 h

1000 h Static Exposure Example

Scribe

Panels

End Exposure

Scrape Test

Start Salt Fog

Exposure

24 h

1000 h Dynamic Exposure Example

1. Stop Exposure

Scrape Test

2. Continue

Exposure

1. Stop Exposure

Scrape Test

2. Continue

Exposure

1. Stop Exposure

Scrape Test

2. Continue

Exposure

250 h 250 h 250 h 250 h

Outline







Key Takeaways

Performance Testing on Cold Rolled Steel (CRS)

150 μm Scribe

150 μm Scribe

500 μm Scribe500 μm Scribe

Self-healingControl

Coating: Zinc-rich primer (>85 wt% zinc)

(SSPC Paint 20 Level 1)

DFT: 3 mils

Substrate: 3”x5” lightly abraded CRS

Capsule Size: 10μm

Application Method: Conventional Spray

Exposure Time: 250 h

Test: ASTM B117 exposure, Scrape 250 h

Note: Coatings were applied via

manufacturer’s specifications.

Control System





(CRS)

Microencapsulated



0

2

4

6

8

10

12

14

150 500

Ad

hes

ion

Lo

ss

fro

m S

cri

be

(m

m)

Scribe Width (microns)

Control

Control + 4wt% AMPARMOR™ 2000Self-healing

Control


150 μm Scribe

150 μm Scribe


Control

Coating: Zinc-rich primer (>85 wt% zinc)


DFT: 3 mils


Capsule Size: 10μm






0

2

4

6

8

10

12

14

16

150 500

Ad

hes

ion

Lo

ss

fro

m S

cri

be

(m

m)

Scribe Width (microns)

Control

Control + 4wt% AMPARMOR™ 2000

Control System





(CRS)

Microencapsulated



Self-healing

Self-healing

Control


150 μm Scribe

150 μm Scribe


Control

Coating: Zinc-rich primer (77-85 wt% zinc)


DFT: 3 mils


Capsule Size: 10μm






0

2

4

6

8

10

12

14

16

150 500

Ad

hes

ion

Lo

ss

fro

m S

cri

be

(m

m)

Scribe Width (Microns)

Control


Control System





(CRS)

Microencapsulated



Self-healing

Self-healing

Control


150 μm Scribe

150 μm Scribe


Control

Coating: Zinc-rich primer (77-85 wt% zinc)


DFT: 3 mils


Capsule Size: 10μm






0

2

4

6

8

10

12

14

16

18

20

150 500

Ad

hes

ion

Lo

ss

fro

m S

cri

be

(m

m)

Scribe Width (Microns)

Control


Control System





(CRS)

Microencapsulated



Self-healing

Self-healing

Control

Performance Testing on Blasted Steel

Coating: Zinc-rich primer (70-80 wt% zinc) (SSPC Paint 20 Level 2) DFT: 3 mils

Substrate: Blasted Steel Capsule Size: 10μm


Test: ASTM B117 exposure followed by adhesion loss evaluation

Note: Coatings were applied via manufacturer’s specifications.

2000

Outline







Key Takeaways


Control System





(CRS)

Microencapsulated



Build Coat Coat: 2K Solvent-Borne Epoxy


Coating: Zinc-rich primer (> 80 wt% zinc), epoxy

polyamide (topcoat)

DFT: Zinc Coat - 3 mils, Epoxy Coat - 8 mils, (11

mils total)


Capsule Size: 10μm




Note: Coatings were applied via manufacturer’s

specifications.

Control Zinc +

Epoxy Second Coat



Self-healing Zinc +

Epoxy Second Coat

0

2

4

6

8

10

12

14

16

18

156μm 500μm

Ad

hesio

n L

oss f

rom

Scri

be

(mm

)

Scribe Width

9100 Control

9100 4wt%Control + 4 wt%

AMPARMORTM 2000

Control

Self-healing

Control

Performance Testing on Blasted Steel

Coating: Zinc-rich primer (> 80 wt% zinc), epoxy

polyamide topcoat)

DFT: Zinc Coat - 3 mils, Epoxy Coat - 8 mils, (11

mils total)

Substrate: 4”x6” 16ga SSPC SP10 Blasted Steel

Capsule Size: 10μm




Notes: Coatings were applied via manufacturer’s

specifications.

Control + 4 wt%

AMPARMORTM 2000

Control Zinc +

Epoxy Second Coat

Self-healing Zinc +

Epoxy Second Coat

150 μm Scribe 150 μm Scribe


Control

Control System


Substrate: Blasted Steel


Substrate: Blasted SteelMicroencapsulated





0

5

10

15

20

25

156μm 500μm

Ad

hesio

n L

oss F

rom

Scri

be (

mm

)

Scribe Width

9100 Control

9100 4wt%Self-healing

Control

Outline







Key Takeaways

Key Takeaways

Performance

Only true self-healing system for protective and high-performance coatings

No external intervention required for effective healing response

Versatility

Microencapsulation approach facilitates application in a variety of existing coating

formulations without the need for any synthetic modification to resin

Multiple chemistries increase chemical compatibility

Transportation Oil & Gas Industrial MaintenanceMachinery/Equipment

MilitaryInfrastructureAlternative Energy Consumer

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