Study of passivation treatment on SS321 electrolyte reservoir used in AgO-Zn reserve battery, for defence applications

Abstract

SS321 is used as the electrolyte reservoir to store potassium hydroxide electrolyte. The metal is prone to get corroded at the electrolyte environment. The present work is carried out for minimizing the corrosion of SS321 potassium hydroxide electrolyte reservoir which is a part of the AgO-Zn reserve primary battery by passivation with citric acid. The uniqueness of the present work exhibits the optimization of passivation method and process conditions, to withstand concentrated alkaline (KOH) medium stored in SS321 electrolyte reservoir, which is having a long life of more than 7 years. Polarization and KOH resistance tests suggest that AISI 321 showed excellent passivation studies behavior when treated with citric acid solution. Hence it is necessary to establish the corrosion behavior of SS321 electrolyte storage container in alkaline solution by electrochemical studies. The thickness loss and weight loss are the main parameters measured to quantify the amount of corrosion. The Voltammetry and AFM studies established the minimum corrosion rate by passivation process method. Based on the results of electrochemical studies and anodic polarization experiments, it was confirmed that the passivation layer formed by treating the material with Citric acid, is capable of improving the corrosion resistance of stainless steel significantly and the passive film is more stable than those produced by other passivating methods. Thus, to minimize the rate of corrosion on electrolyte storage container for the period of battery life of more than 7 years, citric acid passivation having a good corrosion resistance in concentrated alkaline electrolyte (KOH) medium, is best suited and the method of treatment involved is benign & environment friendly.