Materials Performance Supplements

CORTEC 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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FIGURE 2 Control panels failed after 168 h in the salt fog cabinet. such as polyethylene films, foams, pow- ders, and liquids to provide a vapor phase of corrosion protection without impacting the environment. Experimental Procedures This study examines the effectiveness of various types of corrosion inhibitors in a waterborne styrenated acrylic coating, based on salt fog results (ASTM B117 7 ). All of the samples were made using high-speed dispersion. Each coating was applied in triplicate on 4 by 12-in cold-rolled steel (CRS) panels (SAE 1010), using a 40 RDS † draw down bar. This produced a dry film thickness (DFT) of 1.0 mils +/– 0.2 mils. Tables 1 and 2 show the list of prepared samples. Testing Procedures Pan el s were prepared according to ASTM B117 and allowed to cure at ambient temperature for seven days. After the cur- ing cycle, the panels were scribed with a single diagonal scribe per ASTM D1654. 8 All of the edges and backs of the panels were taped to prevent any corrosion creep from uncoated surfaces. Panels were then placed in a 5% sodium chloride (NaCl) salt fog chamber, per ASTM B117. The test panels were checked periodically for blisters, creep from scribe, and degree of rusting. Results The purpose of this experiment was to investigate the effectiveness of nano-VCIs when added to waterborne acrylics. The ultimate goal was to achieve 1,000 h in a salt fog chamber (ASTM B117), on CRS, with a high gloss clearcoat of less than 2.0 mils DFT. Normally this kind of performance can only be achieved with highly pigmented coatings using corrosion inhibitors that are toxic, or at the very least not environmen- tally friendly. The control panels failed at approxi- mately 168 h in the salt fog cabinet, as can be seen in Figure 2 and Table 3. Figure 3 and Table 4 show the results of the 700-h salt fog test; Figure 4 and Table 5 show the results at 1,000 h. Coatings With the DoD estimat- ing that corrosion costs in the military are in excess of $20 billion, there is a n e e d f o r e n v i r o n m e n - tally friendly, low v ola- tile organic compounds, waterborne coatings that can be applied at a thin film thickness (1.0 mils) TABLE 1. LIST OF COATING FORMULATIONS Sample No. Description Corrosion Inhibitor Percent of total formula weight (%) Coating thickness (mils) 1 Control D 0 0.9-1.2 2 Exp. 1 A 3 0.9-1.2 3 Exp. 3 A+C 5 0.9-1.2 4 Exp. 2 B 3 0.9-1.2 5 Exp. 4 B+C 3 0.9-1.2 TABLE 2. CORROSION INHIBITOR DETAIL Corrosion Inhibitor Description D Organic/inorganic corrosion inhibitor A Amino carboxylate salt A+C Amino carboxylate salt + nano-inhibitor B Liquid sol gel B+C Liquid sol gel + nano-inhibitor TABLE 3. ASTM B117, 168 H SALT FOG RESISTANCE Sample No. Film Thickness (mils) Corrosion Rating (A) Scribe Rust (B) 1 0.9-1.2 5 5 2 0.9-1.2 8 5 3 0.9-1.2 9 9 4 0.9-1.2 8 8 5 0.9-1.2 10 10 ( A) ASTM D1654, Procedure B rating of unscribed areas: 10 = no corrosion, 5 = 11 to 20% corrosion, 0 = 75%+ corrosion. (B) ASTM D1654, Procedure A rating of failure at scribe: 10 = no creepage, 5 = 0.125-0.1875 in., 0 = 0.625+ in. † Trade name. 21 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2017

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