nathan kofira technical development ... - corrosion inhibitors
TRANSCRIPT
Overview
1
2
3
4 Formulating with Anti-Corrosives
Corrosion Inhibitor Selection
Mechanisms of Corrosion
Types of Corrosion in Coatings
5 Temporary Rust Prevention
Examples of Corrosion Processes
Flash Rust
Galvanic
Filiform
Rapid, widespread corrosion seen during initial application.
Contact between two alloys which promotes oxidation of the less noble metal.
Differential aeration promotes this unique form of corrosion.
Of concern in coatings…
Flash rust is a rapidly forming corrosion event that typically manifests itself during application or shortly thereafter. The same driving force behind this can lead to ‘in-can’ chime rust.
Fe Fe Fe Fe Fe Fe Fe
R
NH2
H2O
R
NO2-
NO2-
H2O H2O
R
H N H H N H
NO2- N
Fe+2 4e-
H2O
H2O
Chemisorption Oxidation
Short Term Corrosion Inhibition
Galvanic Corrosion Inhibition
Flash Rust Inhibited
Galvanic & Flash Rust Inhibition
Uninhibited
Sodium Nitrite
HALOX® 515
Weld Seams
Control Extender Pigments
Filiform corrosion is efficiently controlled through the combined use of both an Ion Exchange Inhibitor and Organic Acid Inhibitor.
9% Ion Exchange Inhibitor 2% HALOX® 650
Filiform Corrosion Inhibition 1.2mil Epoxy primer with 2mil Polyurethane topcoat on Aluminum.
500hrs. Filiform Corrosion Test
Corrosion Inhibitors A material deposited as a
film on a metal surface that either provides physical protection against corrosive attack or reduces the open-circuit potential difference between local anodes and cathodes and increases the polarization of the former.
.. Any of a number of materials used to prevent the oxidation of metals
Mechanisms of Corrosion Inhibition
Ion Exchange
Anodic Passivation
Hydrophobicity
Ambiodic (Mixed)
Cathodic Passivation
Precipitation
Vapor Phase
Sacrificial
Anodic Reaction ● Slow the reaction rate of anodic dissolution. ● Produce reaction products which form a thin film
over anode. Cathodic Reaction
● Disrupt the flow of electrons from the anode to the cathode.
● Produce reaction products which precipitate selectively at cathodic sites.
Corrosion Inhibitors must impact one of the two elements of the corrosion cycle.
Non-Toxic Inorganic Inhibitors
Commonly Used Inhibitors Zinc Phosphate Modified Zinc Phosphate Complex Phosphosilicate Modified Borates Complex Borosilicates
Composition of Inhibitors [Zn3 (PO4)2 • 2H2O] [M* • Zn3 (PO4)2 • 2H2O] [M* • P2O5 • SiO2 • XH2O] [M* • B2O3 • XH2O] [M* • B2O3 • SiO2 • XH2O]
M* may represent one of more of the following metals; Calcium, Barium, Strontium, Molybdenum, Aluminum.
Passivation Mechanism
+
+
+
+
+
+
-- -
-
--
+
-
Zn3(PO4)2
+
-
Hydrolysis
Anode
Insoluble FePO4
Cathode e-
Fe2+ H2O
Precipitate Mx(OH)x
Substrate Fe
Transition from Zinc Phosphate to Zn+2 Free
Increased Barrier Properties
Anodic Passivation
Passivation & Ion exchange
HALOX® CW-491
Z-PLEX 111
HALOX® 750
HALOX® CW-2230 HALOX® SW-111
HALOX® 430
HALOX® 430 JM Passivation
Reduced Zn+2
Zn+2 Free
Zn+2 Free
+
+
+
+
+
+
-- -
-
--
+
-
Barrier enhancement, lower Zn+2
1032 hrs. Salt Spray
1344 hrs. Prohesion
5% Z-PLEX 111 5% Zinc Phosphate
WB Acrylic on CRS; 2mil; PVC 25%
Synergy of Hybrid Inhibitor
Improved Wet Adhesion
Reduced Blistering
5% Zinc Phosphate 5% HALOX® 750 5% Modified ZnPhos
W/R Acrylic mod. Alkyd on Bonderite 1000; 400hrs. Salt Spray; 2.4mil
Organic Acid Anodic Inhibitors
Key Benefits
Improved Adhesion
Associative with additives
and pigments
Improved gloss retention
Reduced H2O permeability
Key Features
Wetting out of substrate
Stabilization of soluble corrosion products
Liquid products
No Ionic crosslinking
Passivation with Organics
6mos. Marine Exposure
2K Epoxy primer with PU topcoat on CRS; 2mil each
By using HALOX® 630 in place of Zinc Phosphate, the water sensitivity of the film greatly improved.
15% Zinc Phosphate 4% HALOX® 630
Organic Amine Cathodic Inhibitors
Key Benefits
Mechanism is independent of dissolved O2
Associative with additives
and pigments
Potential replacement for Flash Rust inhibitors with added long term protection!
Key Features
Barrier to electron diffusion at Cathode
Stabilization of soluble corrosion products
Displacement of water
High binding energy
Synergy with Inorganic Inhibitors
5% HALOX® 430
Control 1% HALOX® 515 0% Organic
STY/Acrylic on CRS; 500hrs. Salt Spray; 2mil
Formulating Advice
BLISTERING
GELATION
SEEDING
VISCOSITY Δ •Consider the Oil Adsorption when selecting the level and type of dispersant.
•Utilize HALOX® Organic CI’s to lessen impact of Inorganic charge density.
•Examine the overall loading level of plasticizers and coalescents.
•Examine the water sensitivity and solubility of paint additives.
Water Based Acrylics may exhibit some of the following symptoms when replacing the existing corrosion inhibitor system.
Dispersant Selection
5% HALOX® SZP-391
1% HALOX® 570
Control TAMOL 165 A Disperse-Ayd W 22
STY/Acrylic on CRS; 336hrs. Salt Spray; <100g/L VOC; 2.2mil
Formulating Advice
BLISTERING
GELATION
SEEDING
VISCOSITY Δ •Stability can be achieved by adding a coupling solvent or increasing the level of strong amine.
•Pay attention to order of addition or increase the level of strong amine.
•Examine the overall loading level of plasticizer and coalescent.
•Balance the level of strong amine with weak amine or use amine containing HALOX® Organic CI’s.
Water Reducible and Modified Alkyds may exhibit some of the following symptoms when replacing the existing corrosion inhibitor system.
Amine Selection
Balancing Stability and Performance
W/R Epoxy Ester on CRS; 336hrs. Salt Spray; 1.5mil
Weeks at 50°C
75/25 50/50 25/75 100
1
2 3
4
3 4
At first glance, panel 4 appears to suffer from deficient corrosion protection, underlying cause is hydrolysis which can be corrected through amine modification.
Formulating Advice
BLOOMING
GELATION
APPEARANCE
POT LIFE Δ •Minimize ionic crosslinking.
•Balance the cure time and the polymer fluidity to achieve optimal film formation.
•Select a solvent which promotes low viscosity as crosslinking progresses.
•Monitor and adjust dwell time and temperature.
Solvent Borne and Hi-Solids Epoxies may exhibit some of the following symptoms when replacing the existing corrosion inhibitor system.
Fully developed formulations and technical assistance are available at
www.halox.com
Before arriving at this formula, we experimented with a number
of options, searching for the right corrosion inhibitor.
Impacts to pot life and corrosion performance were most critical
in making the final decision.
Obtaining Formulating Advice
Final SPF has less Zn+2
Low Zn+2 /Organic Hybrid yields good pot life and corrosion protection.
7% ZAM Plus 7% HALOX® 750 7% HALOX® SZP-391
2K High Solids Epoxy on CRS; 1000hrs. Salt Spray; 2mil
2K Waterborne Epoxy
Identifying the most critical aspects of your coating leads to one of the many
offerings.
HALOX®
550 WF HALOX®
430 JM HALOX® SZP-391 JM
HALOX®
CW-491
Key Features of HALOX® 430 & 430 JM
Ion Exchange and Passivation
Heavy Metal Free Synergy with Organic Inhibitors in thin films
Corrosion Inhibitor Comparison
Control
2K Epoxy Dispersion on CRS; 1000hrs. Salt Spray; 3.5mil; PVC=34%
8% HALOX®
CW-491 8% WC-213 8% CAPP 8% AC-5 5% HALOX®
430
1K Waterborne Epoxy
Opportunities to explore SYNERGY with Organic inhibitors increase
formulating latitude.
HALOX®
550 WF HALOX®
750 HALOX®
SW-111
Key Features and Benefits of HALOX® 750
Built In Synergy ● Inorganic/Organic Hybrid
Multi-System Performance ● Use in Water and Solvent Borne Systems
Excellent Passivation Outstanding Blister Resistance Enhanced Barrier Properties
Thin Film Applications
Film thickness, adhesion, and gloss are typically the most critical parameters.
HALOX®
550 WF HALOX®
430 JM HALOX® SZP-391 JM
Synergy With
Organics
60° Gloss
60° Gloss
Jet Milled Inorganics
HALOX®
SZP-391
HALOX®
SZP-391 JM
3% 6%
W/R Alkyd on CRS; 336hrs. Salt Spray; 1mil
80.7 60.8
80.7 82.7
Key Features of HALOX® 550 WF
Adhesion Promoter and Corrosion Inhibitor Additive for Protective Primers
● General purpose ● High Gloss DTM coatings ● Wash Primers ● Clearcoats
Multi-Substrate Performance ● Galvalume - Improved Black Rust mitigation ● HDG - Improved White Rust mitigation
Emulsifiable Rust Preventative
Temporary protection for ferrous and non-ferrous metals.
Does NOT need to be removed before coating!
HALOX® 900 NOT a water displacing solvent blend!
NOT an oily coating!
NOT a resin or wax coating!
Emulsifiable Rust Preventative
No need to rinse before coating! Pretreatment yields better adhesion at the scribe and fewer blisters.
168 hrs. Salt Spray
672 hrs. QUV/Prohesion
2 cycles
HALOX® 900 without
Estimated Indoor Storage Interval
Water
Dilution
by Volume
2 15 20
Up to 1 week 1 week to 3 months 3 – 6 months 6 months to 1 year
98
HALOX® 900 can be easily emulsified over a wide range. Dilute the concentrated product under agitation with water to achieve the desired level of rust prevention.
85 80
10
90
HALOX® 900 concentrate
Estimated Outdoor Storage Interval
Water
Dilution
by Volume
2 15 20
Up to 1 week 1 – 2 weeks 3 – 6 months <6 months
98
In dry, covered locations, HALOX® 900 may provide rust prevention prior to coating.
85 80
10
90
HALOX® 900 concentrate
