A Study of Corrosion Resistance and Fatigue Strength of Inert Gas Arc and Oxyacetylene Welds of Al-Mg-Mn Alloy

Abstract

The corrosion resistance of inert-gas arc and oxyacetylene welds of Al-Mg-Mn alloy against an aqueous solution of 7% NaCl plus 3% H₂O₂, was studied by observing the progress of corrosion attack, weight loss, electrolytic solution potential, tensile properties and fatigue strength. The result is summarized as follows ;
(1) The corrosion attack on inert-gas tungsten-arc (TIG) weld and inert-gas metal-arc (MIG) weld was especially remarkable at the toe of weld, while the attack on oxyacetylene weld was over-all pitting on bead surface.
(2) The corrosion weight loss of TIG weld was the greatest among the three welds, however, there was not appreciable difference between MIG and oxyacetylene welds.
(3) The effect of the two attack on tensile properties was almost negligible as far 144 hours immersion was concerned.
(4) The as-welded fatigue strength after a repeated bending cycle of N=2×10⁶ was 10.5kg/mm² (80% of that of the base metal) in TIG weld, 10kg/mm² (77% of base) in MIG weld and 9kg/mm² (70 % of base) in oxpacetylene weld. However, the fatigue strengths 2×10⁶ cycle of the three welds were decreased to the same value, 8 kg/mm² (60% of base metal) after 144 hours immersion which caused 5 to 15% reduction in effective volume.