Comparison of electrochemical porosity test methods for TiN-coated stainless steel

Abstract

Porosity is virtually unavoidable in thin coatings deposited on metal surfaces. This work compares various electrochemical porosity test techniques for TiN-coated stainless steels. The corrosivity of test process, which represents the degree of corrosion of stainless steel after a particular electrochemical test process, is used as the basis for comparison. Three electrochemical techniques are examined for porosity measurement in H 2SO 4 solutions containing KSCN: the anodic current ratio, a coulometric method and a porosity calculation from E corr and R p measurement. The common characteristic of test results is that porosity indexes obtained by various methods decrease with decreasing corrosivity of the test process , and approach constant values. These constant values of porosity indexes, which are obtained at test conditions that cause little damage to TiN coatings, are close to each other and should represent the accurate porosity value of this TiN-coated sample. This work reveals that different electrochemical porosity test techniques can achieve a similar result for porosity measurements on TiN-coated stainless steels.