Effect of NaCl concentration, pH value and tensile stress on the galvanic corrosion behavior of 5050 aluminum alloy

Abstract

The effects of NaCl concentration, solution pH value and tensile stress on galvanic corrosion behavior of 5050 aluminum alloy coupled to 45 steel were investigated using a zero resistance ammeter. The influence and mechanism of various factors in the galvanic corrosion process were studied using electrochemical technology. The results show that there are large potential differences between 5050 aluminum alloy and 45 steel, and they have high galvanic corrosion tendency when making up a galvanic couple. The galvanic corrosion increases with increasing NaCl concentration, with decreasing pH of the solution and with increasing tensile stress applied on the material. In distilled water, the 5050 aluminum alloy potential is low at the beginning of test, resulting in the 5050 alloy acting as an anode and suffering corrosion. As the reaction progresses, the 5050 alloy's potential gradually increases and may exceed that of 45 steel. At this time, the electrode polarity reversal occurs and the 5050 aluminum alloy becomes the cathode. When the solution pH value is 2, the passive film loses its protective function for the matrix, resulting in serious corrosion. Tensile stress causes passive film breakdown on the 5050 aluminum alloy surface and increases the electrochemical potential, resulting in the increase of galvanic corrosion potential difference and serious galvanic corrosion.