Chemical Conversion Coatings on Aluminum Substrate with the Bath Containing MgSO<sub>4</sub>

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Other Title
  • 硫酸マグネシウム添加浴によるアルミニウムの化成処理皮膜
  • リュウサン マグネシウム テンカヨク ニ ヨル アルミニウム ノ カセイ ショ

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Description

Chemical conversion coatings formed with dilute solutions containing MgSO4 and NaHCO3 to improve the corrosion resistance of aluminum were discussed. A porous layer of the basic salt of Al and Mg was deposited uniformly on the Al substrate, and this film of ca. 4-7μm thick was identified to be Al·aMg·b(SO4)·c(OH)·dH2O, of which electrical resistance was high. When the specimen was chemically treated, the corrosion potential of aluminum moved to the negative direction whereas the pitting potential became positive. As a consequence, the corrosion resistance is improved extensively. Sulfate ions existing in neutral solutions of sodium chloride inhibited the adsorption of chloride ions on the film, and the pitting potential was moved to the positive direction. The film thus obtained was more resistant to the corrosion than the boehmite film in chloride solutions containing cupric ions.

Journal

  • CORROSION ENGINEERING

    CORROSION ENGINEERING 37 (9), 553-558, 1988

    Japan Society of Corrosion Engineering

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