INHIBITION OF NST-44 MILD STEEL CORROSION BY SOME INORGANIC SUBSTANCES IN 0.1M AMMONIUM NITRATE SOLUTIONS

M. Alagbe

Department of Metallurgical Engineering

Kwara State Polytechnic, Ilorin, Nigeria

E-mail: alagbemic@yahoo.com

Abstract: This study presents the report of an investigation on the effect of sodium nitrite (NaN0₂), sodium biphosphate (Na₂HP0₄), potassium chromate (k₂Cr0₄), potassium dichromate (k₂Cr₂0₇) and sodium benzoate (C₆H₅COONa) inhibitors on the corrosion characteristics of NST-44 mild steel in 0.1M ammonium nitrate solutions.  The corrosion rates of the exposed mild steel were obtained using the weight loss immersion method.  It was observed that oxidizing inhibitors like sodium nitrite, potassium chromate and potassium dichromate were more efficient than non-oxidizing inhibitors like sodium biphosphate and sodium benzoate by providing inhibition at molar concentrations of 5 x 10^-3M and 5 x 10^-2M respectively in 0.1M ammonium nitrate solutions. The results obtained on cold-work and various inhibitors indicate that cold working increased adsorption of inhibitors.  Smaller quantities of inhibitors were therefore needed to inhibit corrosion of cold-worked mild steel than in un-worked sample.  The results of this research are expected to improve the corrosion resistance of this steel as a constructional material for fertilizers, dyes and explosives processing industries in Nigeria.