ORIAKHI NOSA

Welding is the process to join two or more similar or dissimilar metal with the applicationofheat and sometime pressure. Gas Tungsten Arc Welding (GTAW) is commonly knownasTungsten Inert Gas Welding (TIG Welding). Corrosion of metal is an ubiquitous phenomenonthat occurs in various forms. Atmospheric or uniform, galvanic, crevice, pitting, and microbial corrosion are most familiar forms of corrosion. The service life of engineering structuresisaffected by the quality and strength of the welded joints. The effects of corrosion affects thequality of the welded joints and the general structure. The offshore structures are exposedtothevarious environments, and it is well known that the corrosion rate and the corrosion mechanismunder each environment, marine atmosphere, splash zone, tidal zone, underwater zoneandbottom zone, are different. The aim of this study is to model the environmental effectsofcorrosion on tungsten inert gas weld joints of a mild steel pipe using response surfacemethodology. Mild steel pipe was cut into dimension 40mm in length, 12mm diameter and 3mmthickwithapower hacksaw, grinded and cleaned before the welding process. The experimental matrixwasmade of twenty (20) runs, generated by the design expert software adopting the central composite design. The response was measured, which is the rate of corrosion and then modelledusing the response surface methodology. The result obtained in this study shows that the current has a very strong influence on the rateofcorrosion. Based on the findings, it is summarized that the corrosion rate is minimumwhenawelding voltage of V = 18V, current = 120A and gas flow rate = 13lit/min. The response surfacemethodology employs certain statistical tools which are Anova, goodness of fit, coefficient ofdetermination and noise to signal ratio which determines the adequacy and significance of themodel developed. The result from this study shows that the model has a very good varianceinflation factor and p-value < 0.05. The model posseses favourable coefficient of correlation(R)value for the rate of corrosion