Materials Performance Supplements


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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Environmental Advantages of VCIs Over Traditional Inhibitors Traditional inhibitors containing heavy metals, nitrites, or secondary amines or banned materials such as dicyclohexylammo- nium nitrite are becoming increasingly more regulated and often are no longer allowed to be used due to the negative impact they have on the environment and carcinogenic effects on workers exposed to them. The environ- mental advantages of using VCIs are that they are nontoxic, do not contain heavy metals, and have no adverse effect due to their low usage concentrations. VCIs have long been used in other products such as polyethylene films, foams, powders, and liquids to provide a vapor phase of corrosion protection without impacting the environment. Removal of Temporary Coatings Removal of temporary coatings can be done using environmentally friendly alkaline cleaners. These cleaners are typically diluted in water at a relatively low concentration (2 to 20%), sprayed or brushed onto the coated sur- face, and allowed to dwell for a period of 5 to 15 minutes. The coating is then removed using a hot water wash (120 to 180 °F [49 to 82 °C]). Experiments These studies examine the effectiveness of various types of corrosion inhibitors in solvent and waterborne removable coat- ings, based on salt fog results (ASTM B117 6 ) and humidity results (ASTM D1748 7 ). ASTM B117 tests products in a 5% sodium chlo- ride (NaCl) salt fog chamber with continu- ous exposure. ASTM D1748 tests products in a 120 °F, 95% relative humidity chamber with continuous exposure. Each coating was applied on cold rolled steel panels (SAE 1010) obtained from an industry supplier of test panels. The panels provided are pre-cleaned test panels that are ready to use without any additional surface preparation required. In some cases, coat- ings were applied to actual parts provided by customers. Dry film thicknesses (DFTs) were according to the manufacturer's recommen- dations (Figure 3, 4, 5, and 6). FIGURE 3 Salt spray testing for solvent-borne wax coating without and with VCIs. FIGURE 4 Humidity testing for solvent-borne wax coating without and with VCIs. FIGURE 5 Salt spray (ASTM B117) testing for various systems (600 h). ASTM B117 350 h Without VCI (A) 400 h With VCI (A) 50 h Without VCI (B) >400 h With VCI (A) ASTM B117 ASTM C1748 3,170 h Without VCI (A) >3,170 h With VCI (A) 1,100 h Without VCI (B) >3,170 h With VCI (A) ASTM C1748 A Solvent-borne coating without VCI B Solvent-borne coating without VCI C Waterborne coating with VCI FIGURE 6 Humidity testing for solvent-borne wax coating and waterborne wax coating with VCIs (768 h). 17 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2018

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