Abstract
Over the past few years there have been several instances in the oil and gas industry of incompatibilities and failures of stainless steel components carrying or containing chemical products. Material of construction compatibility with chemical products is a vital assessment to ensure asset integrity of critical components is maintained during field operation. The focus of this paper is on the evaluation of neat chemical product compatibility with stainless steel 316L, UNS S31603 (SS316L), a commonly employed metallurgy for storage tanks and umbilical tubing. A typical approach to assess the compatibility of stainless steel with neat chemical products involves using a weight-loss immersion corrosion test methodology. However, this procedure has the inherent limitation in that it can take a long time to conduct whilst data interpretation can be difficult since the induction period for pitting is unknown.
This paper presents and discusses data from accelerated stainless steel compatibility tests of various neat chemical products with SS316L using anodic cyclic potentiodynamic polarisation at both 20 0C and 55 0C. Criteria based on electrochemical characteristics from polarisation curves, which were generated within a timeframe of only a few hours, have been established to assess the likelihood of stainless steel compatibility fully immersed in various neat chemical products. It was found that those products which resulted in SS316L having both a pitting potential, Epit, of more than 200 mV above the open-circuit potential (OCP) and a current density at 150 mV, i150mV OCP, of less than 5 µA cm-2 from anodic potentiodynamic polarisation conducted using a potential sweep rate of 10 mV min-1 (0.166 mV s-1) were found to be compatible in long-term immersion tests, whilst those products that did not meet these criteria failed long-term compatibility assessment.
