Effect of mechanical loading on the galvanic corrosion behavior of Mg- steel joint

Conference Dates

July 15-20, 2018


Here a time dependent numerical model aimed to investigate the role of mechanical deformation on the corrosion behavior of galvanic joint is developed. The influence of mechanical loading on the corrosion behavior of the AE44 (Magnesium alloy) and mild steel galvanic joint immersed in a 1.6 wt% NaCl solution is explored across a wide range of combined mechanical and electrochemical conditions. It is shown that the presence of mechanical loads on the galvanic couple was found to cause an increase in both the peak and average pit depth. However, there was a noticeable increase in the peak pit depth due to the presence of plastic strain near the galvanic junction. Further, the presence of tensile loads was found to increase the tendency for localized corrosion around the galvanic junction for both the electrochemical scenarios: a) decreasing electrolyte depth; and b) larger cathodic surface area. For tensile loads greater than 60 MPa, a transition from the slow propagating corrosion pit regime (electrochemically dominated) to a rapid crack propagation (mechanically dominated) was predicted to take place within 60 hours of immersion in 1.6 wt% NaCl solution. Finally, the accumulation of equivalent strain of 3.5% ahead of the corrosion pit was found to correspond to the fracture of the galvanic joint. Overall, the findings presented here highlight the complex interactions that occur between the mechanical and electrochemical processes during stress-assisted corrosion of galvanic joints. Therefore, this systematic investigation provides a robust numerical framework for accurate examination of the role of mechanical deformation on the corrosion behavior of structural alloys. In particular, the model described here may be useful for designing, developing and ranking the structural galvanic joints that are exposed to combined mechanical and electrochemical processes.

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