Prediction the Initiation of Pitting Corrosion Depending on Carbides in the Microstructure of 304 Stainless Steel

Abstract

Stainless steel has excellent corrosion resistance due to formation oxides protective films in many environments. When steel exposed to temperature in the range of (500-900) ºC, the carbon in the structure will be effective to react with chromium in the structure , which is no less than 18.6% in the present used steel, to form chromium carbides in different types (M23C6, M7C3, M2.9C) in which M represent chromium. Therefore pitting corrosion will be initiated due to two reasi, the first was depleted zone and the second is galvanic effects between carbides and matrix. The present work was aimed to find relationships to predict the initiation of pitting corrosion depending on carbides in the microstructure of 304 stainless steel, which formed in heated specimens at (500 - 900) ºC. The potentiodynamic cyclic polarization (PCP) measurement was performed to investigate and analyze pitting corrosion resistance properties.