Effect of ferric ions in AISI 316L stainless steel pickling using an environmentally-friendly H2SO4-HF-H2O2 mixture

Abstract

Austenitic stainless steels (SS) are alloys widely used in many applications where high corrosion resistance materials are required, e.g., petrochemicals industries. The influence of iron (ferric) ions in the pickling of AISI 316L SS was studied using an environmentally-friendly chemical treatment based on sulfuric-hydrofluoric peroxide mixtures. p-Toluene sulfonic acid (PTSA) had a positive influence on H2O2 stabilization during the first 4 days of experimentation. Temperature and the stirring parameter in the pickling bath had a negative effect on H2O2 stability. Ferric ions had a negative effect on H stability, and a threshold might be defined above which the H2O2 loss increased. Pickling of AISI 316L SS could be performed using the environmentally-friendly H2O2 mixture. The AISI 316L SS pickling rate decreased from 2.6 mg/sq dm day (mdd) in the absence of ferric ions to 0.2 mdd in the presence of 40 g/L ferric ions for 1 hr at 50°C.