| 摘要 |
PURPOSE: To secure sufficient adhesiveness while reducing the thickness of a plating film as compared with the conventional one by forming a thermally sprayed coating on the surface of a plating layer whose surface is activated by means of nitric acid etching or sand blasting treatment applied to the material surface. CONSTITUTION: For example, a material 1 composed of cast Al alloy is alkali-degreased, water-washed, and then immersed in a mixed acid liquor consisting of hydrofluoric acid and nitric acid in a 1:3 ratio to undergo the removal of smut resulting from the alkali treatment, followed by water washing. This material is immersed in a zinc displacement liquor to precipitate metallic zinc in the surface of Al, followed by water washing. After this material is immersed in a nitric acid liquor at room temp. to peel off the zinc displacement film, a secondary zinc displacement is applied, by which a displacement film is made dense and adhesiveness and coating power are improved. After water washing, this material is immersed in the zinc displacement liquor again in order to improve adhesiveness, followed by water washing. Then, plating of Ni-P-SiC, etc., is applied to this material to form a dispersion plating layer 2 of about 60μm thickness. Nitric acid etching or sand blasting treatment is applied to this surface to remove an oxide layer 3 to activate the surface. Subsequently, this surface is plasma-thermal-sprayed with thermal spraying material of metal, such as Ni and Cr, or metal oxide.
|
