The corrosion behaviour of type 316L stainless steel in aqueous 30-50 wt%. NaOH at temperatures up to 90 °C has been elucidated. Exposure to room temperature environment showed parabolic weight loss behaviour, with corrosion rates of up to 0.4 mm/year. Higher NaOH concentrations and exposure temperatures resulted in a reduced stability of the electrochemical passivity domain, associated with higher corrosion rates. Exposure to de-aerated 50 wt%. NaOH presented corrosion rates of up to 0.5 mm/year at open circuit potential, with maximum corrosion rates under polarisation of up to ≈ 18 mm/year. The formation of a dark iron-oxy-hydroxide and nickel-oxide was observed, with exposure to temperatures in excess of 50 °C. The behaviour of type 316L stainless steel in hot caustic environment is compared to types 204, 304, 2205 stainless steel, and nickel alloy 200.

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The corrosion propagation rate during natural exposure tests of powder-coated steel and the relationship between natural exposure and accelerated cyclic corrosion testing (ISO 20340) results were investigated. Generally, during natural exposure, an initial fast increase in the corrosion area followed by a period where the corroded area grows very slowly are observed. As a consequence, the relative ranking between coating systems varies significantly as a function of test time. Correlation between natural exposure results and cyclic test results was not found; in many cases, a better performance in one test is associated with a worst performance in the other.