Localized Corrosion: An Empirical Approach to the Study of Passive Film Breakdown Rates

Abstract

Electrochemical tests lasting 600 h to 6,000 h, at different potentials, were carried out on Type 316L (UNS S31603), Type 904L (UNS N08904), and nickel alloy 825 (UNS N08895) in sodium chloride (NaCl) solutions. A statistical approach was adopted using samples of 10 to 60 specimens. The pitting or crevice corrosion behavior was reported using cumulative frequency of passive film breakdown vs. time. In this work, we considered the formation of stable occluded cells as the breakdown of passive film. Each corrosion system “passive alloy-environment-geometry-time” was characterized by straight lines (i.e., breakdown rate of passive film, ρb), with a higher slope in the initial stage and a lower slope after some tens/hundreds of hours. The ρb can be used in the design for material selection and industrial maintenance schedules.

Electrochemical methods for the determination of Pedeferri's diagram of stainless steel in chloride containing environment

“…Configuration No. 2 : This sample holder is supposed to limit the crevice effect based on previous experience . Samples were cut from plates in 2 × 3 cm size.…”

Electrochemical Scanning Tunneling Microscopy (ECSTM) – From Theory to Future Applications

“…Normally, this initial process leads to a number of parallel electrochemical methods that result in material dissolution and/or eventual formation of secondary corrosion products. Basically the metal corrosion processes can be classified in two different forms: one is general corrosion [36] that symbolizes those corrosion processes involving the entire surface area of the material, and the second one localized corrosion [37] which mentions to a number of corrosion processes that are triggered at specifics sites on the material surface. The presence of a surface passive film prevents the metallic substrate from further oxidation, i.e., the surface becomes passivated.…”

Simulation of pit interactions of multi-pit corrosion under an anticorrosive coating with a three-dimensional cellular automata model

“…In addition, the probability of Although some previous research suggests that the breakdown rate of the anticorrosive coating may not be constant in some conditions (e.g. [6,50]), in this paper, for simplicity, we assume that the area of anticorrosive coating that is breakdown is proportional to time. Then the probability of breakdown of every C site is approximately independent from each other.…”