Improvement of tribological behavior of stainless steels in food cleaning process by sodium hydrogen carbonate

Stainless steel pumps in food industries are prone to seizure during sanitation operations. To understand the tribocorrosion phenomena induced during the cleaning routine, tribological and tribocorrosion tests were carried out using three inexpensive, eco-friendly domestic cleaning solutions: 8 % acetic acid, and 5 % sodium hydrogen carbonate. Some tests were conducted in demineralized water, which served as a reference medium. High friction and wear were observed with AISI 316 L stainless steel in vinegar and water, consistent with current observations in food cleaning processes. However, in sodium hydrogen carbonate, an unprecedented tribological behavior was recorded under specific test conditions. Worn surface analysis results indicate that this phenomenon is associated with the formation of a passive film composed of chromium oxides/hydroxides and iron oxides/hydroxides, with the emergence of a nickel-rich sublayer. The electrical activity of the passive film demonstrated its insulating behavior. Due to the synergistic interactions between the mechanical wear of the passive film and chemical reactions of AISI 316L stainless steel in sodium hydrogen carbonate, significant improvement in the frictional properties of AISI 316L has been found, which can play an important role in increasing the mechanical life of equipment and energy efficiency.