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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
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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
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Corrosion Inhibitor Chemistries
Organic
Mixed
(Hybrid)
Inorganic
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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
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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
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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
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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
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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
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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
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Adsorption
e- e-
H+ H+
Fe2+
OOO
FeFeO
O
O
O
O
O O
O
2Fe --> 2Fe2+ + 4e-
Surface layer
BTSA
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Flash Rust & In-Can Corrosion
0.5% BTSA0.2% BTSA
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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
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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)
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Adhesion Promotion
Binder
Substrate
BTSA can improve
adhesion between
Primer/Topcoat
interface (intercoat)
Binder/Substrate
interface (adhesion)
Pigment/Coating
interface (coupling)
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Adhesion Promoter (Coating/Coating)
Improved inter-coat adhesion between aged and new
coating layers
Coating/Coating interface
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Adhesion Promoter (Coating/Substrate)
Resin Organic Corrosion Inhibitor
Improved adhesion between coating and metal substrate
Coating/Substrate interface
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Adhesion Promotion
Loss of adhesion on
Galvanized steel after salt spray
336 hrs NSS; 50 micron DFT
Organic corrosion
inhibitor
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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
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Pore Plugging
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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)
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Increased Hydrophobicity (Barrier)
Higher temperature (170-
200 C) stable molecule,
suitable for bake systems
10% Zinc
Phosphate4% BTSA
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Increased Hydrophobicity (Barrier)
4% BTSA
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Reduced Water Uptake (Barrier)
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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
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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
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Contact Information:
Phone: 219-933-1571