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Study of Microbial Induced Corrosion of Aluminum Alloy with Micro-arc Oxidation

Author: ZhaoYong
Tutor: LiuHongFang
School: Huazhong University of Science and Technology
Course: Applied Chemistry
Keywords: Sulfate-reducing bacteria Aluminum alloy Micro-arc oxidation Rareearth conversion Hormesis effect
CLC: TG178
Type: Master's thesis
Year: 2012
Downloads: 35
Quote: 0
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Abstract


Owing to its excellent light weight, high strength and cheap price, aluminumalloy are widely used in the electronic products, automobile industry, shipbuildingindustry, construction industry, mechanical manufacturing, offshore industry,aerospace industry and some other industries. However, aluminum alloy can not beused directly for its poor corrosion resistance. With reports of the aircraft accident bythe cause of microbial corrosion increasing, people pay more attention to theanti-corrosion methods for the existence of microorganism.In this paper, we used the methods of ultraviolet spectrophotometry （UVS）,cyclic anodic polarization, electrochemical impedance spectroscopy（EIS） and surfaceanalysis techniques（Scanning electron microscopy and epi-fluorescence microscopy,EFM） to study the effect of rare earth Ce to the growth of sulfate reducingbacteria（SRB）. We also studied the microbial induced corrosion （MIC） behavior ofaluminum alloy LY12CZ under different concentrations of rare earth Ce. Furthermore,we also studied the MIC of aluminum alloy with micro-arc oxidation （MAO）. Themain progress and results are listed as follows:1．The results of UVS showed that it promoted the growth of SRB when theconcentrations of rare earth Ce3+was0.376mg·L-1.But when it was more than1.13mg·L-1, the growth of SRB was inhibited. By using the cyclic anodic polarizationcurves and EIS, the anti-corrosion property of aluminum alloy which caused by rareearth in culture medium with and without SRB was studied. Meanwhile, themorphology of matrix after coupon tests was observed by SEM and EFM. Cyclicanodic polarization curves showed that the pitting sensitivity of aluminum alloybecame lower in the solutions containing rare earth Ce3+. EIS results showed that SRBincreased the corrosion of aluminum alloy. In culture medium, with an increase in theconcentration of Ce3+, the charge transfer resistance increased also. When inoculatedwith1%SRB, because of a synergistic effect between the biofilm and the rare earthconversion film, the charge transfer resistance was the biggest when the concentration of rare earth Ce3+was0.376mg·L-1.2．By tracking the open circuit potential, monitoring pH, EIS, polarization curvesand SEM, the anti-corrosion property of aluminum alloy with different thickness ofMAO coating was studied. The results indicated that SRB can be found on the surfaceof the matrix with MAO by EFM. The adsorption of SRB to the loose layer of MAOcoating increased corrosion. Therefore, compared with30μm micro-arc oxidation film,the matrix with80μm micro-arc oxidation had a better ability to inhibit MIC.3．The corrosive properties of welding butts were investigated by weight lossmethod and SEM. In the immersion test, the results indicated that the anti-corrosionproperties in the weld nugget zone was the best compared with heat affect zone.Micro-arc oxidation can significantly improve the change of anti-corrosion propertiescaused by the welding thermal stress.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > The corrosion of various metals and alloys,corrosion and surface treatment
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