Effect of Scribing Modes on Corrosion Test Results

Abstract

A Prohesion salt spray corrosion test was carried out with 32 primer-coated AA2024-T3 (UNS A92024) test panels with four different kinds of scribes (eight test panels each). The scribing width and depth showed little effect on the test results. The extent of damage to the interface between the primer and the substrate alloy produced the greatest influence on the test results. The concurrent electrochemical impedance spectroscopy (EIS) measurement with Prohesion salt spray showed that the sharp drop of the impedance modulus at low frequency (|Z|0.1Hz) for the samples scribed with a spinning cutter tip started much earlier during the Prohesion exposure than for samples scribed without spinning the cutter tip. There was very little difference observed on the impedance modulus values of the samples with different scribe depth and width. The consistent results between the Prohesion test results and EIS data suggest that the concurrent EIS measurement with Prohesion salt spray may provide additional information pertinent to the corrosion protection mechanisms involved in the coating under examination.