Effect of Welding on Pitting and Intergranular Corrosion Behavior of Marine Grade Aluminum Alloy

AA 5052 H32 aluminum alloy is one of the most commonly used materials in the marine environment due to its good formability, good weldability, and better corrosion resistance. Assessment of resistance of welds of the alloy against corrosion is necessary for reliable design. In the present study, pitting and intergranular corrosion behavior of tungsten inert gas (TIG), normal friction stir welding (FSW), and underwater FSW (UFSW) joints of AA 5052 H32 aluminum alloy and parent alloy are investigated. Electrochemical corrosion behavior by Tafel polarization technique and intergranular corrosion susceptibility by mass loss of the specimen in concentrated nitric acid solution are studied as per ASTM standards. The corrosion studies were conducted on welded plates for which welding parameters during TIG welding and FSW were kept optimum for maximum tensile strength. The result shows that corrosion resistance of welded joints is inferior to that of parent metals. Corrosion resistance of the FSW joint and UFSW joint are nearly equal and found to be higher compared with the TIG joint. Density and size of pits formed on the parent metal and welded joints are examined via macro- and microscopic analysis and atomic force microscopic study. Results also show that the specimens welded by FSW and UFSW processes are immune to intergranular corrosion attack.