ISSN 2305-6894

The protective properties of conversion coatings on 1424 alloy upon oxidation under various conditions

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A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, Moscow, 119071 Russian Federation

Abstract: The influence of parameters of chemical oxidation of lithium-containing aluminum alloy 1424 in chromate-free IFHANAL-3 conversion formulation on the properties of the conversion coatings formed was investigated. After standard pretreatment (grinding, etching and desmutting), the alloy samples were oxidized in IFHANAL-3 with addition of Trilon B and benzotriazole. The coatings thus obtained were filled in a solution of the corrosion inhibitor. The protective ability of the conversion coatings (CC) obtained was determined from the length of the passivity domain on the anodic polarization curves in chloride-containing borate buffer. The length of the passivity domain qualitatively correlates with the time of alloy oxidation and, accordingly, with the CC thickness. A decrease in the oxidation temperature affects the weakening of the protective ability of the CC less strongly than a decrease in the pH of the conversion formulation. It is shown that on repeated use of the conversion formulation, the CC formed on alloy 1424 has consistently high protective properties. At the same time, the thickness of the coatings even slightly increases due to the accumulation in the oxidation solution of the products of alloy dissolution. Filling of the coatings obtained in solutions containing various amounts of the corrosion inhibitor showed a significant effect on CC hydration. This is supported by the increase in the specific weight gain of the coating after its filling with an increase of the inhibitor concentration in the filling solution.

Keywords: aluminum alloys, conversion coatings, filling of coatings, corrosion inhibitor

Int. J. Corros. Scale Inhib., , 2, 268-274 PDF (437 K)
doi: 10.17675/2305-6894-2019-8-2-8

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