| As the lightest metal structure material at present,magnesium alloy has a great application prospect in the fields of automobile transportation,aerospace and electronic products.However,the poor corrosion resistance seriously restricts the large scale application of magnesium alloys.In addition to common physics corrosion element such as temperature and stress et al,microorganisms can also cause influence on corrosion of magnesium alloys and their protective coatings.In this paper,the influence of Pseudomonas aeruginosa on the corrosion behavior of AZ91D magnesium alloy and micro-arc oxidation coating was investigated,and the influence mechanism was also discussed,which enriched the research of magnesium alloy in the field of microbiologically influenced corrosion.The corrosion behaviors of AZ91D magnesium alloy in sterile and bacteria inoculated environments were compared by immersion test and corrosion electrochemical test.The results showed that the corrosion rate of AZ91D magnesium alloy in aseptic environment was 0.13±0.01 mm/a,the corrosion type was uniform corrosion;in the presence of Pseudomonas aeruginosa,the corrosion rate increased to 0.23±0.01 mm/a,and the surface showed local corrosion characteristics.In sterile environment,the corrosion of AZ91D magnesium alloy was gradually inhibited by the accumulation of corrosion product layer.In the presence of bacteria,Pseudomonas aeruginosa will adhere to the surface of magnesium alloy and form an uneven bio film,whose growth and metabolism will accelerate the damage of corrosion product film,accelerating the corrosion of AZ91D magnesium alloy.The potentiodynamic polarization curves showed that Pseudomonas aeruginosa accelerates the shedding of? phase by promoting cathodic hydrogen evolution,accelerating the corrosion of AZ91D magnesium alloy.In addition,the micro-arc oxidation coating and nano-CuO doped micro-arc oxidation coating with thickness of about 30 ?m were prepared on the surface of AZ91D magnesium alloy by silicate electrolyte,and the influence of Pseudomonas aeruginosa on the corrosion behavior of the two coatings was investigated.The results showed that the surface of micro-arc oxidation coating was gray and white,and the coating turned black and red after doped with nano-CuO particles,and nano-CuO particles mainly assembled on the surface of the coating.Pseudomonas aeruginosa accelerates the corrosion of micro-arc oxidation coating and nano-CuO doped microarc oxidation coating by promoting the cathodic hydrogen evolution reaction at the matrix interface of AZ91D magnesium alloy.After doped nano-CuO particles,the surface of micro-arc oxidation coating had more holes,resulting in slightly lower corrosion resistance of nano-CuO doped micro-arc oxidation coating than that of undoped micro-arc oxidation coating. |
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