Atmospheric Corrosion of Welded Mild Steel

Abstract

Mild steel is commonly used for structural purposes in Mauritius. Arc welding is one of the main joining methods used, with Manual Metal Arc (MMA), Metal Inert Gas (MIG) and Tungsten Inert Gas (TIG) welding techniques being the preferred ones. This paper compares the corrosion resistance of mild steel, joined using these welding techniques. Mild steel samples, welded using MMA, MIG and TIG welding techniques, were exposed outdoors for a very short duration of 9 days, according to ASTM G50, and subjected to alternative immersion tests, according to ASTM G44, for 130 cycles. For the atmospheric exposure tests, digital image processing techniques were used to determine the amount of corrosion in the samples. For the alternate immersion tests, the weight loss method was used. The results of the three welding techniques were then compared. The microstructure of the weld area was also analysed to this end. For the atmospheric exposures, it was observed that the MIG welded specimens suffered from preferential weld corrosion, whereas for the TIG welded specimens, the welded area corroded the least. For the alternative immersion tests, it was again observed that the MIG welded samples were less corrosion-resistant compared to the other samples. Also, the TIG welded specimens were found to be the most corrosion resistant.