Quantitative Model for the Prediction of the Corrosion Rate of Cold-Rolled 316L STEEL

The austenitic stainless steel 316L is used for numerous components due to its excellent corrosion resistance. However, forming of components influences the microstructure and can thus change the corrosion resistance of the steel. In this context, the corrosion rate of the steel 316L is determined for the case of uniform corrosion of various cold-rolled conditions by ageing tests in 0.5 M H₂SO₄. The microstrain, the martensite fraction, and the residual stress state are quantified using X-ray diffraction. The surface roughness is measured by laser scanning microscopy. Three different model equations are derived by means of multiple regression to predict the corrosion rate as a function of the specimen properties. The analysis shows that a particularly simple model equation, which predicts the corrosion rate only via the plastic strain, shows insufficiently large deviations from the experimentally determined corrosion rates. However, a low divergence to the experimental results with a mean deviation of less than 4% is achieved by using a model equation that takes microstructural parameters and the surface ratio into account. Within this model equation, an increased corrosion rate is achieved with higher microstrain and residual compressive stress of the austenite phase as well as a higher surface-area ratio. A higher fraction of martensite is found to lower the corrosion rate.