Statistical analysis of the repeatability of the crevice corrosion repassivation potential

Abstract

An extensive database of crevice corrosion repassivation potentials (ER,CREV) of corrosion-resistant and high-temperature alloys was analysed with statistical tools. Repeatability of results, which considers multiple tests performed by the same team with the same experimental setup, was assessed. Evaluated variables include those that allegedly affect the outcome of testing techniques used to determine ER,CREV such as crevice formers material, applied torque, the extent of corrosion propagation before repassivation and electrochemical procedures; and environmental and metallurgical conditions that may change the corrosion susceptibility of materials such as thermal ageing, alloy composition, temperature, chloride concentration and inhibitors. Guidelines to decide on the significance of changes in crevice corrosion repassivation potentials are proposed. Analysis of collected data suggests that a sample size of 5 is appropriate for assessing any change in the environmental or metallurgical conditions on the repassivation potential.