TO EXAMINE CORROSION RESISTANCE of aluminum alloys for automobiles, we used accelerated corrosion test, that was 5% salt spray test and alternate immersion test in 5% NaCl solution and 4.7% CaCl2 solution.
Aluminum alloys used in these tests were 2036, 5182, 6061, 7016 and AC4C with several finishes. In comparision with aluminum alloys, cold rolled steel sheets, HSLA steel and galvanized steel sheets were used.
The results of these test showed that aluminum alloys generated shallow pitting corrosion and steels generated large amount of corrosion products. The large amount of corrosion in bare steel specimens causes to reduce its tensile strength. In case of weld-bonded (spot-welded) specimens, there developed galvanic and crevice corrosion, especially galvanic corrosion exhibited on the side of aluminum alloys.
We also examined the difference among these test methods. The results of the alternate immersion test in 5% NaCl solution were very similar to 5% salt spray test and the alternate immersion test in CaCl2 solution generated deeper pittings on aluminum specimens than in NaCl solution.