Corrosion of Stainless Steel During Acetate Production

Corrosion of types 304, 304L, 316, and 316L (UNS S30400, S30403, S31600, and S31603, respectively) stainless steel (SS) during the esterification of acetic acid (CH₃COOH) and alcohol or glycol ether was investigated. The catalyst for this reaction, sulfuric acid (H₂SO₄) or para-toluenesulfonic acid (PTSA), was shown to cause more corrosion on reactor equipment than CH₃COOH under the process conditions commonly practiced in industry. The corrosive action of the catalyst occurred only in the presence of water. Thus, for the batch processes, corrosion occurred mostly during the initial stage of esterification, where water produced by the reaction created an aqueous environment. After water was distilled off, the corrosion rate declined to a negligible value. The corrosion inhibitor copper sulfate (CuSO₄), often used in industrial acetate processes, was found to work well for a low-temperature process (< 95°C) such as in production of butyl acetate, but it accelerated corrosion in the glycol ether acetate processes where temperatures were > 108°C. Process conditions that imparted low corrosion rates were determined.