Strictly confidential - proprietary information of HALOX

www.halox.com

Multifunctional Organic Corrosion

Inhibitors for Environmentally

Compliant Coatings

Andrew Balgeman

www.halox.com

2

HALOX Overview

Corrosion Background

Traditional Noncompliant Corrosion Inhibitors

Challenges for EC coatings

Chemistry of Organic Corrosion inhibitors

Multifunctional Features» Flash Rust Prevention

» Anodic Passivation

» Adhesion Promotion

» Pore Plugging

» Reduce Water Uptake (Barrier)

Conclusion

www.halox.com

3

Corrosion Inhibitors

Materials deposited as a

film on a metal surface that:

(1) Either provide physical

protection against corrosive

attack

(2) Reduce the open-circuit

potential (OCP) difference

between local anodes and

cathodes

(3) Are used to prevent the

oxidation of metals

www.halox.com

4

Corrosion Inhibitor Chemistries

Organic

Mixed

(Hybrid)

Inorganic

www.halox.com

5

Challenges for Environmentally

Compliant Coatings

Toxicity: Replacing toxic corrosion inhibitors with non

toxic materials that are equally effective

Cost: Toxic materials are inherently less expensive and

more widely used

Raw material availability: need to create an awareness of

nontoxic materials available in the market as toxic

materials are being phased out

Formulation know-how: Substituting toxic materials with

these organic corrosion inhibitors requires an

understanding of their chemistry and how to properly

incorporate these products into coatings

www.halox.com

6

Traditional Non-Compliant

Corrosion Inhibitors

Inorganic

Corrosion

Inhibitors

Chromate

salts

Zinc

salts

Barium

salts

Nitrites &

Nitrates

Risk

(Humans)High Low Low High

Risk

(Environment)High High

Aquatic toxin

Harmful if inhaled

or swallowed

High

www.halox.com

7

Phosphatization

»Contain heavy metals (Ni, Mn, Zn)

»Eutrophication caused by phosphates

»Examples: Bonderite

»NY Bans Phosphorus in Detergent,

& Lawn Fertilizer (Chem Insider Daily 8/16/10)

Chromatization

»Contains toxic heavy metals (not compliant

with REACH, RoHs, WEEE, ELV)

»Toxic to environment and humans

»Examples: Alodine

Traditional Non-Compliant

Corrosion Inhibitors

www.halox.com

8

Chemistry of Organic Corrosion

Inhibitors

Esters of benzothiazol-2-

ylthio succinic acid (BTSA)

Multiple functional groups

present on structure

Molecule can be tailored

through chemical reactions

Solubility can be controlled

for use in coatings

O

O-

O

O-

S

S

N

www.halox.com

9

Functional Groups

O

O-

O

O-

S

S

N

(1)

(2)

(4)

(3)

(1) Polar end: adsorption & strong

affinity for M+/ MO leading to

hydrophobic dense film

formation. Also the Acid -Base

reactivity site for modification

(2) Electron donor site

(3) Polycyclic aromatic: corrosion

inhibition of non-ferrous

substrates. Electron donors (N,

S, O)

(4) Non polar end: van der Waals

interaction with multiple organic

binders (Compatibility). Also

electron donor to substrate

BTSA

www.halox.com

10

Flash Rust Inhibition

NH4+

NH4+

O

O-

O

O-

S

S

N

O

O-

O

O-

S

S

N

Base neutralization of

BTSA makes product

water soluble in coatings

above pH 7

Environmentally effective

substitute for nitrites

Adsorption of carboxylic

acid on Fe substrate

prevents flash rust in WB

coatings (passivation)

NH4OH

www.halox.com

11

Adsorption

e- e-

H+ H+

Fe2+

OOO

FeFeO

O

O

O

O

O O

O

2Fe --> 2Fe2+ + 4e-

Surface layer

BTSA

www.halox.com

12

Flash Rust & In-Can Corrosion

0.5% BTSA0.2% BTSA

www.halox.com

13

Anodic Passivation

O

O-

O

O-

S

S

N

Adsorption of molecule

forms a complex which

increases the electrical

resistance of the substrate

Makes the oxidation of

steel more difficult

A form of active corrosion

protection

www.halox.com

14

0.01 M BTSA inhibitor

0.12 M NaClO4

pH 7.5, 25 C

Low Carbon Steel

Area: 15 cm2

O

HO

O

OH

S

S

N

Anodic Passivation

Positive potential shift (anodic)

www.halox.com

15

Adhesion Promotion

Binder

Substrate

BTSA can improve

adhesion between

Primer/Topcoat

interface (intercoat)

Binder/Substrate

interface (adhesion)

Pigment/Coating

interface (coupling)

www.halox.com

16

Adhesion Promoter (Coating/Coating)

Improved inter-coat adhesion between aged and new

coating layers

Coating/Coating interface

www.halox.com

17

Adhesion Promoter (Coating/Substrate)

Resin Organic Corrosion Inhibitor

Improved adhesion between coating and metal substrate

Coating/Substrate interface

www.halox.com

18

Adhesion Promotion

Loss of adhesion on

Galvanized steel after salt spray

336 hrs NSS; 50 micron DFT

Organic corrosion

inhibitor

www.halox.com

19

Pore Plugging

Adsorption of molecule

reduces moisture access

to substrate

Electrolyte access to

pores and defects blocked

by bulky constituents

Leading to better barrier

protection

www.halox.com

20

Pore Plugging

www.halox.com

21

Increased Hydrophobicity (Barrier)

Molecule can be reacted

with bulky amine groups to

create a more hydrophobic

corrosion inhibitor

Control water solubility

Reduce water permeation

in coatings

Increase temperature

stability of molecule for

higher temperature coatings

(e.g. bake primers)

www.halox.com

22

Increased Hydrophobicity (Barrier)

Higher temperature (170-

200 C) stable molecule,

suitable for bake systems

10% Zinc

Phosphate4% BTSA

www.halox.com

23

Increased Hydrophobicity (Barrier)

4% BTSA

www.halox.com

24

Reduced Water Uptake (Barrier)

www.halox.com

25

Reduced Water Uptake (Barrier)

No

Inhibitor

4% BTTSA-

amine0 0 0

3

4

2

55

2

3

65 5

4

4

25

2

4

15

2

4

31

0

5

4

4

55

4

4

45

7

4

51

5

5

7

4

35

6

4

45

9

4

52

0

6

2

4

36

1

4

46

2

4

32

5

6

2

4

26

3

4

36

3

4

13

0

6

5

4

0

WATER PERMEATION OF 2K-EPOXY PRIMERS

0

1

0

2

0

3

0

4

0

5

0

6

0

7

0

0 5 1

0

1

5

2

0

2

5

3

0TIME (days)

WA

TE

R P

ER

ME

AT

ION

(%

)

No Inhibitor

4% organic corrosion inhibitor

The change in

Capacitance can be used

to calculate the water

uptake in a coating under

immersion conditions.

%v = 100log(CC,0 / CC,24)

log(80)

Volume fraction of water

www.halox.com

26

Conclusion

BTSA molecule provides multifunctional features in

combating corrosion in environmentally compliant coatings

BTSA molecule can be tailored through simple chemical

reactions for use in WB and SB systems, as well as

Powder Coating applications

BTSA is completely non-toxic!

BTSA

Visit our website at www.halox.com

Contact Information:

abalgeman@halox.com

Phone: 219-933-1571