Studies on properties of rust formed during atmospheric corrosion

The nature of corrosion product has a marked effect in controlling atmosphere corrosion rate. The paper describes some of these changes during the first 2 years' exposure studies undertaken at the National Metallurgical Laboratory. Changes in the composition, constituents and porosity of rust with progress of time were determined in cases of mild steel and low alloy steel using various techniques. Porosity of rust layer was found to decrease with time, the change being more in case of low alloy steel compared to mild steel. The analysis of rust indicated that the change in porosity is related to build up of insoluble sulphate in the rust. (Dr. A.K. Lahiri, Mr. K.P. Mukherjee, Mr. S. Rao Addanki, Scientists and Dr. T. Banerjee, Scientist-in-charge, National Metallurgical Laboratory, Jamshedpur)