Effect of hydrazine and formaldehyde on the corrosion of SS 304L in hot nitric acid environment

Electrochemical and immersion tests were carried out for SS 304L at 80 °C in 2 M nitric acid containing hydrazine and formaldehyde. The addition of hydrazine resulted in the higher anodic current and no appreciable change in weight loss. For formaldehyde, the reaction with nitric acid resulted in copious evolution of NO2 gas and the subsequent dissolution of the gas in the solution. The open circuit potential (OCP) shifted to anodic direction by 300 mV. The OCP and polarization behaviour are controlled by the solution chemistry rather than the material surface.