The Prediction of Long-term Coating Performance from Short-term Electrochemical Data, Part II. Comparison of Electrochemical Data to Field Exposure Results for Coatings on Steel

Abstract

The pace of coatings development is limited by the time required to assess their corrosion protection properties. This study takes a step forward from Part I of this series and correlates the corrosion performance of organic coatings assessed by a series of short-term electrochemical measurement with 18-month beachside exposure results of duplicate panels. A series of 19 coating systems on A36 steel substrates were tested in a blind study using the damage tolerance test (DTT). In the DTT, a through-film pinhole defect is created, and the electrochemical characteristics of the defect are then monitored over the next 4 to 7 days while immersed in 0.5M NaCl. The results from open circuit potential, anodic potentiostatic polarization, and electrochemical impedance spectroscopy were used to characterize the corrosion behavior of the coating systems. The beachside exposure tests were conducted at the Kennedy Space Center according to ASTM D610-01. It was found that for 79% of the coatings systems examined, the 18 month beachside exposure results could be predicted by two independent laboratory tests obtained within 7 days.