Four types of coatings were examined for corrosion resistance in three separate environments. The coatings included electrocoat paint on galvanized steel, galvanized steel, electrocoat paint on bare steel and pre-painted steel. The corrosion resistance of the coatings was evaluated on automobile automatic transmission oil pans. Three test methods, including salt spray, accelerated corrosion test track testing and customer vehicles, were evaluated. The electrocoated paint on galvanized steel provided the best corrosion protection of the four types examined because pierced barrier coatings expose the galvanized underlayer which then provides continuing protection. The other barrier coatings allowed the bare steel to be exposed with subsequent corrosive attack. The galvanized coating offered protection but only until the zinc transformed into a non-adherent coating. The most informative and most severe test method was found to be the accelerated corrosion test and the least informative was the salt spray.

Subject
Accelerated corrosion tests, Test methods, Zinc rich coatings, Spray coating, Galvanized coatings, Customers, Galvanized steel, Salt spray corrosion testing, Steel, Rust, Corrosion resistance, Barrier coatings, Paints
Keywords:
Coatings, Galvanized, Electrocoat, Paint, Corrosion, Salt Spray, Accelerated, Correlation
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1995
Association for Materials Protection and Performance (AMPP)
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