METHOD FOR MANUFACTURING COATED STEEL WITH HIGH RESISTANCE AGAINST CORROSION UNDER SALT DAMAGE ENVIRONMENT

• Main Author: HAMAHARA KYOKO
• Format: Patent
• Language: English; Japanese
• Published: 11.06.2015
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; LAYERED PRODUCTS; LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT ORNON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM; METALLURGY; PERFORMING OPERATIONS; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSPORTING

PROBLEM TO BE SOLVED: To provide a method for manufacturing a coated steel with a single coating (one-coat one-bake) having high resistance against corrosion under a harsh corrosive environment such as a salt damage environment.SOLUTION: A method for manufacturing a coated steel includes: preparing a base material of hot-dip zinc-5% aluminum alloy-coated steel; performing chemical conversion treatment on the base material with a phosphate treatment solution having an appropriate amount of a free acid content to form a phosphate-based treatment film by reaction; and performing coating treatment on the processed base material with a coating containing an organic resin to form a single coating film as an upper layer of the processed base material. The phosphate treatment solution contains appropriate amounts of a water-soluble phosphoric acid compound, a water-soluble nitric acid compound, a water-soluble zinc compound, and a water-soluble nickel compound, and has a free acid content of 0.3 to 0.9 point. The coated steel with a single coating prevents blistering of coating under a harsh corrosive environment such as a salt damage environment, exerts high corrosion resistance after coating, and ensures durability as high as that of a double coating. 【課題】一層の塗膜形成（１コート１ベーク）で塩害環境のような、厳しい腐食環境下においても優れた耐食性を有する塗装鋼材の製造方法の提供。【解決手段】溶融Zn−5％Al合金めっき鋼材を基材とし、該基材に遊離酸含有量を適正範囲に調整したリン酸塩処理液による化成処理を施し、リン酸塩系成処理皮膜を反応形成し、さらにその上層として塗膜を、有機樹脂を含む塗料による塗装処理を施して１層の塗膜を形成した塗装鋼材とする。なお、リン酸塩処理液は、適正量の、水溶性リン酸化合物、水溶性硝酸化合物、水溶性亜鉛化合物、水溶性ニッケル化合物等を含み、遊離酸を0.3〜0.9ポイントに調整した水溶液とすることが好ましい。【効果】これにより、塩害環境のような厳しい腐食環境においても、塗膜フクレの発生を防止でき、塗装後耐食性に優れ、しかも、２コート塗装と同等の耐久性を１コート塗装処理で確保できる。【選択図】なし