| LIN Bi-lan.Corrosion Resistance of Phytic Acid Conversion Coating Modified by Molybdate on Aluminum Alloy[J],45(3):115-119 |
| Corrosion Resistance of Phytic Acid Conversion Coating Modified by Molybdate on Aluminum Alloy |
| Received:January 21, 2016 Revised:March 20, 2016 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2016.03.019 |
| KeyWord:aluminum alloy corrosion resistance phytic acid molybdate conversion coating |
| Author | Institution |
| LIN Bi-lan |
School of Material Science and Engineering, Xiamen University of Technology, Xiamen , China |
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| Abstract: |
| Objective To further enhance the corrosion resistance of phytic acid conversion coating on aluminum alloy, sodium molybdate (SM) additives, SM pre-treatment and SM post-treatment were applied to modify the process. Methods The corrosion resistance of the modified aluminum alloy in 3.5wt.% NaCl solution was investigated through dynamicpotential polarization test. Results With an increase in concentration of SM additives, the corrosion resistance of phytic acid conversion coating first increases and then decreases, and the corrosion protection efficiency Pe is largest, about 95.5% when SM was 30 g/L, while that is 86.8% when it was without SM additives. For pH6.0 the Pe value reaches to 98.6%, while a larger or a smaller pH (i.e. pH8.0 or pH6.0) is not beneficial to form a more anti-corrosive coating. However, the corrosion resistance of phytic acid conversion coating is seriously impaired by SM post-treatment, and the corrosion current density jcor is substantially increased. SM pretreated can enhance the corrosion resistance of phytic acid conversion coating, and Pe is 98.2%. When SM pretreatment and SM additives were applied meanwhile, the corrosion resistance of phytic acid conversion coating is improved most significantly, jcor is merely 0.042 μA/cm2, decreasing for about two orders of magnitude; the polarization resistance Rp is 222 kΩ•cm2, and Pe is highly up to 99.5%. Conclusion The corrosion resistance of phytic acid conversion coating on aluminum alloy can be largely enhanced by SM additives and SM pre-treatment, and the inhibition efficiency is more outstanding when these two modified schemes were applied simultaneously. However, SM post-treatment can not improve the corrosion resistance of phytic acid coating on aluminum alloy. |
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