Effect of Equal Channel Angular Pressing Process on the Corrosion Behavior of Type 316L Stainless Steel in Ringer's Solution

The corrosion behavior of metallic biomaterials is an important characteristic because of its strong relationship to the biocompatibility of biomedical grade metallic implants. The goal of this research was to study the effect of the equal channel angular pressing (ECAP) process on the corrosion behavior of the AISI Type 316L (UNS S31603) austenitic stainless steel. Up to eight passes of ECAP were performed on AISI 316L stainless steel samples. A scanning transmission electron microscopy technique was utilized to study the microstructure of the as-received material and the samples subjected to ECAP. Electrochemical corrosion polarization and electrochemical impedance spectroscopy tests were performed in Ringer's solution to determine and compare the corrosion behavior of initial coarse-grained and ECAP specimens as an indication of biocompatibility. An ultrafine-grained nanocrystalline Type 316L stainless steel with a mean grain size of about 78 nm was obtained after eight passes of ECAP were performed. The corrosion resistance of Type 316L stainless steel was improved considerably by increasing the number of ECAP passes. After eight passes of the ECAP process, the corrosion rate of Type 316L stainless steel was measured to be 0.42 μA·cm², which is significantly lower than that of the initial coarse-grained material (3.12 μA·cm²).