Influence and Simulation Study of Surface Coating Damage on Pitting Corrosion of 7B04 Aluminum Alloy

Abstract

Self-corrosion and pitting corrosion of 7B04 aluminum alloy at different environment conditions were studied by electrochemical test with simulating surface coating damage on 7B04 aluminum alloy. The forming conditions of pitting corrosion after contacting 7B04 aluminum alloy with TA15 titanium alloy were analyzed by finite element method which was based on the mathematical model of galvanic corrosion. The results indicate that the pitting potential of 7B04 aluminum alloy is influenced by Cl- concentration and pH value. Pitting corrosion of 7B04 aluminum alloy in self-corrosion condition can occur in neutral solution(mass fraction of NaCl>5%) or in acidic solution(mass fraction of NaCl=3.5%). The potential rises when 7B04 aluminum alloy contacts with TA15 titanium alloy which results in the occurrence probability of pitting corrosion. The occurrence probability of pitting corrosion is increased. The pitting corrosion of 7B04 aluminum alloy initiates and propagates when the area ratio of cathode and anode is greater than 40 in neutral solution(mass fraction of NaCl=3.5%). The potential of 7B04 aluminum alloy decreases slowly with the increase of the distance between cathode and anode, and the decline of the potential is not over 2 mV at distance within 10 m.

Keywords

• 7B04 aluminum alloy
• pitting corrosion
• coating damage
• numerical calculation
• galvanic corrosion