Validated numerical modeling of galvanic corrosion of zinc and aluminum coatings

• Numerical simulations of galvanic corrosion of zinc and aluminum coatings on steel.
• Simulations were compared to profilometry and potential measurements.
• Qualitative patterns of corrosion agreed closely with model predictions.
• Good quantitative agreement was found initially for both coatings.
• Behavior of zinc diverged from the model after 25 min due to loss of reactivity.

A time-dependent finite element model was developed to simulate the corrosion of zinc and aluminum coatings, galvanically coupled to a mild steel substrate in deaerated 0.01 M H2SO4 electrolyte. The simulations of galvanic corrosion for each of the coatings were compared to experimental measurements of open circuit potential, and changes in coating geometry measured via surface profilometry. Good agreement between the model predictions and corrosion tests were observed initially for both coatings. However, in the case of the zinc coating, divergence was observed between the simulation and the corrosion test after approximately 40 min, due to a decrease in the reactivity of the zinc surface.