Overcoming Performance Challenges with Waterborne Primers and DTM

Overcoming Performance Challenges with Waterborne Primers and DTM Coatings Lori Boggs, Ph. D. Technical Team Leader September 20, 2016 1

Outline n Waterborne primers and direct-to-metal coatings n Developing waterborne binders for metal protection n Formulating corrosion-resistant coatings n Application n Testing of primers and DTM coatings 2

Waterborne Direct-to-Metal Coatings n Waterborne acrylic coatings are suitable light duty metal applications for DTM (1 – 2 mils) Metal § Light duty is defined by the C 1 – C 2 categories of the ISO Corrosion standards, ISO 12944 -2 − Corrosion categories C 1/C 2 correspond to a very low to low atmospheric classification − Heated or unheated interior spaces where condensation may occur or exterior environments with low levels of pollution § Industrial maintenance such as pipes, tanks, handrails, steel doors, and rail cars, etc. 3

Waterborne Multi-layer Coatings n Waterborne multi-layer coatings are suitable for medium duty metal applications Topcoat (1 – 2 mils) Primer (2 – 4 mils) Metal § Medium duty is defined by the C 3 categories of the ISO Corrosion standards, ISO 12944 -2 − Production rooms with high humidity and some air pollution, such as food-processing plants, laundries, breweries and dairies. − Urban and industrial atmospheres, moderate sulfur dioxide pollution. Coastal areas with low salinity. 4

Waterborne DTM vs Multi-layer Coatings n Direct-to-Metal (DTM) coatings provide advantages over multi-layer systems in light duty applications by § Reducing the number of application steps − Minimal surface preparation and only one application step § Lowering raw material costs with only one coating layer § Eliminating the need for active pigments (primers typically contain active pigments) n Waterborne acrylic coatings provide high gloss (>80 on a 60° meter), good appearance and corrosion resistance 5

Waterborne Coatings n Waterborne acrylic coatings provide several advantages over solventborne coatings § Better for health and safety with less impact on the environment § Easy clean-up and thinning with water § Low odor, less toxic, and no flammable solvents § Fast drying (ambient conditions or forced dry) which allows for faster recoating times n However, extreme temperature and humidity conditions must be avoided during application for appearance and optimal film formation 6

Developing Waterborne Binders for Metal Protection 7

Developing Waterborne Binders for Metal Protection New development for waterborne binders for metal continue to improve resin performance at reduced VOC AFM images to evaluate Film Formation n A DTM binder is expected to provide corrosion protection without the aid of an anti-corrosive pigment § Waterborne acrylic binders provide corrosion resistance primarily by forming a barrier § Good continuous film formation is critical Surface Phase 8

Developing Waterborne Binders for Metal Protection n A proper choice of binder composition and chemistry is needed to improve barrier properties toward ingression of water and salt § The polymer needs to be hydrophobic and minimize the use of ionic compounds to prevent water from entering the film n A proper design of particle morphology helps with tuning film formation properties while minimizing the use of cosolvents and plasticizers 9

Developing Waterborne Binders for Metal Protection n Resins changes are screened for corrosion resistance 10

Developing Waterborne Binders for Metal Protection Analytical techniques can be used to evaluate the films and predict corrosion performance n Electrochemical Impedance Spectroscopy (EIS) follows the change in capacitance of a coating when submerged in water or an electrolyte to provide information on the barrier properties of the coating § If the impedance stays the same over time, the capacitance is constant and this suggests that the coating is resisting ingression of water and salt § If the impedance drops very fast, water can penetrate into all or part of the coating 11

Developing Waterborne Binders for Metal Protection Microscopy characterization techniques enable following the changes in the structure of the coating while exposed to a corrosive environment n When coupled with Energy Dissipative X-ray spectroscopy (EDX), one can obtain information on how the coating evolves chemically during its service life § EDX allows you to search for different elements like sodium and chlorine on the image while you are taking pictures with the electron beam, so you see a microscopic image and also get information about where each atom is located 12

Formulating Corrosion-Resistant Coatings 13

Formulating Corrosion-Resistant Coatings n The corrosion protection provided by waterborne acrylic coatings is highly dependent on both the resin and the formulation of the coating n Often attempting to drop in or directly replace resins in waterborne formulations does not result in optimum performance n Choosing the appropriate cosolvents, additives, and pigments is necessary to optimize the performance of the coating 14

Formulating Corrosion-Resistant Coatings n Solvent choice § Cosolvent packages need to be optimized for each binder system and are very formulation-dependent § The level of solvent (or plasticizer) required for good coalescence is dependent on the binder § Film formation of the resin alone (or the final coating) may be evaluated with a drawdown on Leneta card, curing at room temperature or in a refrigerator § Properties like water resistance can be affected by the type of solvents § Deionized water is preferred in DTM coatings because the ions in tap water also negatively affect corrosion resistance 15

Solvent Choice n Formula A contains hydrophilic solvents and Formula B contains a plasticizer and more hydrophobic solvents. (Degree of blistering rated according to ASTM D 714) Coalescent Package A 4 -hr dry, overnight immersion, DI Water Polished CRS 4 MD Unpolished CRS 6 D Coalescent Package B 4 -hr dry, overnight immersion, DI Water Polished CRS 10 Unpolished CRS 10 16

Additives n Dispersant A 44 hours Salt Spray Exposure § A very good dispersion of pigments is necessary to avoid agglomeration and resulting film defects that allow penetration of the film § Dispersant choice is critical to corrosion resistance (the more hydrophobic the better) Dispersant B 44 hours Salt Spray Exposure § Compatibility of the dispersant with the binder is also a factor 17

Additives n Defoamers § Necessary to eliminate macro and microfoam to ensure good film formation and defects that would allow water and salt penetration n Wetting agents § More hydrophobic is better for corrosion resistance, if required n Thickeners § Associative non-ionic thickeners like HEUR and HMPE types are preferred for better film formation and to minimize the effect on corrosion n Flash Rust Inhibitors § A flash rust inhibitor like sodium nitrite or an organic corrosion inhibitor is required to prevent flash rust during drying 18

Additives – Surface Active Agents n Additives intended to improve block resistance § Fluorosurfactants and siloxane polymers Resin Additive 1 (Fluorosurfactant) Additive 2 (Fluorosurfactant) Additive 3 (Siloxane polymer) Additive 4 (Siloxane polymer) Resin A 0. 03% 0. 5% Resin B 0. 03% 0. 5% Resin C 0. 03% 0. 5% Resin A 0. 06% 1. 0% Resin B 0. 06% 1. 0% Resin C 0. 06% 1. 0% § Additives were post added to fully formulated paint § DTM coatings were drawn down on plain, unpolished cold rolled steel at 1 or 2 mils dry film thickness (DFT) § Panels were cured at ambient temperature and humidity 19

Additives – Surface Active Agents Block Testing Procedure Coating drawn down on cold rolled steel Coated panels cut into 1 inch x 4 inch strips Strips crossed perpendicularly resulting in a 1 inch 2 contact area Strips pressed down under a 2. 3 lb weight for 30 mins either at RT or 50°C Surface active additives improved the block resistance of the coatings (resin dependent) 20

Additives – Surface Active Agents Salt Spray Results n Panels were subjected to continuous salt fog exposure § 168 hours of exposure for Resins A and B, 72 hours for Resin C § 2 mils DFT films Failure at the Scribe, ASTM D 1654 1 x Additive 6 2 x Additive 5 Rating Rust creepage from the scribe 1 10 0 inches (no creep) 0 4 3⁄16 to 1⁄4 of an inch 0 5⁄8 of an inch or more Rating 4 3 4 ve 3 iti + Ad d ve 2 C + n C es i R n es i R iti ve Ad d iti ve + C n C es i R n es i R Ad d iti in Ad d + R es tiv Ad di + B in 1 C 4 e 3 e 2 tiv e Ad di + B es R in B + Ad di tiv e 1 B in Ad di es R R es in B + R es tiv Ad di A + tiv 4 e 3 e 2 in es R in A + Ad di tiv e 1 tiv e tiv Ad di + A es in es R R es in A + R Ad di in A 2 Salt spray scribe performance not affected for Resins A and C, improved for Resin B 21

Additives – Surface Active Agents Salt Spray Results Degree of Rusting in the Field, ASTM D 610 Resin B + Additive 1 (0. 03%) 10 Resin B + Additive 1 (0. 06%) 8 6 4 2 4 iti ve 3 es i n C + Ad d ve 2 iti ve iti Ad d + R es i n C + C R R es i n C Ad d iti ve 1 C + R R es i n B es R Ad d es in ve + Ad d iti in in 1 x Additive 4 3 ve 2 e tiv Ad d + B es R R es in in es R Ad di iti Ad d B + R iti es in ve 1 B 4 ve 3 es in A + Ad d ve 2 iti ve Ad d iti R in A + Ad d + A es R in es R R es in A + R Ad d iti es i n ve 1 A 0 2 x Additive Rating 10 = Less than 0. 01% surface rusted, 5 = 1 -3% rusted, 0 = Greater than 50% rusted Salt spray field performance not affected for any of the resins 22

Pigments n Titanium Dioxide − Ti. O 2 Grade A 276 hours Salt Spray Exposure § The grade of Ti. O 2 or coating on the titanium dioxide can have a significant effect on the corrosion resistance n Colorant § Dispersed pigments contain surfactants that can also adversely affect the corrosion resistance § Choose colorants recommended for industrial coatings Ti. O 2 Grade B 276 hours Salt Spray Exposure 23

Application 24

Application Films for testing can be prepared by spray application: n Conventional and HVLP air atomized spray § Viscosity of the coating must be reduced to less than 70 KU for atomization § A larger nozzle (1. 9 mm) is preferred § The appearance and film formation of waterborne coatings depends heavily on the temperature and relative humidity conditions n Airless or air-assisted spray 25

Application Films for testing can be prepared by drawdown: n Drawdown bars (Bird bars, Doctor blades, Latex applicator) or wire-wound or wireless rods § The actual wet film thickness depends on the shape of the applicator, the viscosity, surface tension and wetting properties of the coating, and the speed of application § The dry film thickness is approximately equal to the wet film thickness multiplied by the volume solids n Target dry film thickness § DTM coatings: ~2 mils DFT, in one coat § Primers: 2 – 4 mils DFT 26

Application After application, films are allowed to dry at room temperature: n In multilayer systems, primers are applied and allowed to dry at room temperature and topcoat is applied 1 day later n Testing is generally completed in standard conditions: 23°C, 50% relative humidity § Most testing is completed after 7 days of ambient cure § 7 -day testing for DTMs may be accelerated by 1 day of ambient cure followed by 1 hour in a 50°C oven 27

Testing of Primers and DTM Coatings 28

Testing of Primers and DTM Coatings n Substrates for metal coatings: § Cold Rolled Steel, cleaned, unpolished (polished) § Sandblasted Hot Rolled Steel § Cold Rolled Steel with an Iron Phosphate treatment with or without a sealer (chrome or non-chrome) n Standard test panels provide a uniform substrate for testing that minimizes the variation of the steel 29

Testing of Primers and DTM Coatings Corrosion Testing n Continuous Salt Spray (Salt Fog), ASTM B 117 § 5% Na. Cl salt fog at 35°C § Most common and most widely accepted corrosion test, however it does not correlate well with field performance n Panels taped and scribed prior to test § Scribe creep rated according to ASTM D 1654 § Field rust rated according to ASTM D 610 30

Corrosion Testing Salt Spray Testing (ASTM B 117) on a white DTM formula with no anti-corrosive pigments: DFT 1. 5 -2. 0 mils 63 hours SST 184 hours SST 244 hours SST 312 hours SST Polished CRS Unpolished CRS 31

Corrosion Testing Salt Spray Testing (ASTM B 117) on a white DTM formula with no anti-corrosive pigments: DFT 2. 5 -3. 0 mils 63 hours SST 184 hours SST 244 hours SST 312 hours SST Polished CRS Unpolished CRS 32

Corrosion Testing Salt Spray Testing (ASTM B 117) on a waterborne red iron oxide primer/DTM topcoat system: DFT 3 mils/2 mils Waterborne Primer – DTM Topcoat System, 975 hours SST 33

Corrosion Testing Other types of testing that have better correlation to field performance: n Prohesion or Cyclic Salt Spray (Fog), ASTM G 85 -A 5 § 0. 35% ammonium sulfate, 0. 05% sodium chloride § Cyclic: 1 hour salt spray at 25°C, 1 hour dry at 35°C n Combined testing − Cyclic Salt Fog/UV Exposure, ASTM D 5894 § One week Prohesion § Once week QUV: 4 hours UVA (340 nm)/4 hours condensation 34

Corrosion Testing – Salt Spray versus Prohesion Salt Spray 134 hours 278 hours Prohesion 488 hours 960 hours 1279 hours 35

Testing of DTM Coatings n Adhesion Testing, ASTM D 3359 § Dry: Scribe the coating with an X–cut or cross cut, apply tape and pull § Wet: Scribe the coating, cover the scribe with a filter paper, saturate with water and cover with a watch glass, after 60 minutes blot the area dry, apply tape and pull § Rate from 0 – 5 5 = no removal of coatings 0 = >65% removal or beyond the area of the X 36

Adhesion Testing (Rated according to ASTM D 3359, Method B) Wet Adhesion DTM Coating A 30 25 20 8 days wet 15 3 days wet 10 1 day wet 5 8 days dry r- Al 1 day dry Wet Adhesion * 30 25 20 8 days wet 15 3 days wet 10 1 day wet 5 8 days dry 3 days dry 1 day dry Al um in um 0 um Al B 1 07 G H D G EZ 9 X r- 0/ P 9 60 B 1 00 0/ P 00 B 1 *Poor Appearance C H R S sa nd b la st ed d he lis un po S R C R S po lis he d 0 C 3 days dry C DTM Coating B um in um 0 Al um H D B 1 07 G G EZ 9 X 0/ P 9 60 B 1 00 00 0/ P st ed la nd b sa H C R S B 1 d he lis un po R C S R S po lis he d 0 B, P = Bonderite® and Parcolene® are registered trademarks of Henkel Corporation. 37

Testing of DTM Coatings n Water Resistance § Standard Humidity according to ASTM D 2247, 35°C, 100% Relative Humidity chamber § Early Watersoak: coating is allowed to cure for 4 or 8 hours and is then immersed in DI water overnight n Pendulum Hardness § Measures the damping time of an oscillating pendulum § König method, results reported in number of oscillations or time (1. 4 seconds/oscillation) § Relative measure of the hardness of the coating 38

Testing of DTM Coatings n Blocking Resistance § Coatings are drawn down on unpolished cold rolled steel panels with a 3 mil wet bar, allowed to cure for 1 or 7 days and cut into 1. 0 inch strips § The strips are crossed face to face, perpendicular to one another and a 2. 3 lb weight is applied to the crossed panels for 30 minutes at room temperature or in a 50°C oven § Rated according to ASTM D 4946 where 10 = no tack, 4 = very tacky, no seal and 0 = 75 -100% seal 39

Testing of DTM Coatings n Chemical Resistance § Chemicals are applied to a filter paper and covered with a watch glass § After 1 hour the filter paper is removed, the area is blotted to remove the chemical and the coating is scratched and evaluated for softening § The recovery of the coatings is evaluated 24 hours after chemical exposure Formula 409 is a registered trademark of The Clorox Company. Windex is a registered trademark of SC Johnson & Son, Inc. 40

Testing of DTM Coatings n Weathering § QUV (UVA and UVB), WOM and Florida Exposure 6 months exposure 24 months exposure 41

Testing of DTM Coatings n Poor weather performance can result in corrosion as well as loss of gloss 6 months exposure 18 months exposure 42

Conclusions n When formulating waterborne primers or DTM coatings, every component of the formula contributes to the corrosion performance n Binders have been developed that have very good corrosion resistance but must also be formulated for good film formation and with careful selection of additives and pigments n Replacing a resin in an existing formula may not result in optimal performance n Starting point formulations are guidelines for appropriate raw material selections 43

Acknowledgement n Many thanks to Vince Goldman, Ben Langer, Arne Rick, Aditi Chavannavar and Mohsen Soleimani for their contribution and support Questions? 44

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