Salt spray test corrosion protection performance

Salt spray test. The model coatings of Table I are of the high solid type used in automotive top coats. Their primary function is not corrosion protection since this is first of all a matter of phosphate layer, electrocoat and/or primer. However, the topcoats may contribute to corrosion protection by their barrier function for water, oxygen and salts. Therefore their permeability is important as one of the factors in the corrosion protection by the total coating system. We feel that a salt spray test of the model coatings directly applied to a steel surface is of little relevance for their corrosion protection performance in a real system. 

E-coat stripping. Both plasma-treated panels show excellent corrosion protection performance as compared to the control panels. All [2A] panels with different plasma treatments and plasma polymer coatings, which were corrosion tested in both SO2 and Prohesion salt spray tests, were similarly scanned, and the corrosion width was evaluated by using a scanned image and computer calculation of the corroded area. Figure 31.19 compares the corrosion width obtained by the two methods. 

Whether due to the lack of an alternative test method or other reasons, the salt spray test has endured in spite of clear data that, in some cases, it is misapplied and misused, thereby providing erroneous information. As indicated in paragraph 3.2, Prediction of performance in natural environments has seldom been correlated with salt spray results when used as stand alone data. Significance and Use, a modification made to ASTM B 117 in 1985, paragraph X2.2 specifically states, It should be noted that there is usually not a direct relation between salt (fog) resistance and resistance to corrosion in other media because the chemistry of the reactions, including the formation of films and their protective value, frequently varies greatly with the precise conditions encountered. ... 

A series of PANI/sol-gel coating formulations have been applied to an AA2024-T3 substrate and evaluated using electrochemical and salt spray tests. Comparison of the corrosion protection performance of these coatings was made with bare and sol-gel only coated samples. 

Cerium nitrate and cerium chloride with additions of acetylacetone are, according to the salt spray test results, the most efficient corrosion inhibitors, when used as additives to hybrid organic-inorganic coatings. This was also demonstrated by the results of the EIS measurements. Cerium nitrate and, with reservations, cerium chloride in combination with acetylacetone are, according to the salt spray test performance, possible corrosion protection additives to the hybrid coating system used in this study. 

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