Corrosion Tendency of S235 Steel in 3.5% NaCl Solution and Drinking Water During Six Months of Exposure.

The pipeline transport industry is constantly developing due to the high efficiency, long life, varied diameters of the pipelines, but a significant problem is the corrosion that occurs because of the corrosive attack of the various environments in which the pipelines are used. This study deals with the ex situ characterizations (optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray analyses, X-ray diffraction analysis, roughness, and Vickers hardness analyses) and the in situ characterizations (gravimetric and electrochemical methods). Samples of steel were tested at immersion time, after 336 h, 672 h, 1344 h, 2016 h, and 4032 h of exposure to a 3.5% NaCl solution and drinking water. The corrosion rate evaluated with the gravimetric method varied between 0.036518 and 0.008993 mm/year in the 3.5% NaCl solution and 0.02834 and 0.034162 mm/year in drinking water. The electrochemical method resulted in an estimated corrosion rate range of 0.097-0.681 mm/year for the 3.5% NaCl solution, and 0.028-0.0472 mm/year for drinking water. The passivation effect, lifetime, and operating limit of the S235JR steel in the tested corrosive environments were studied. The study can provide technical support to increase the service life of S235JR steel and to predict the suitable environment reduce corrosion costs.