| 摘要 |
Methods and compositions are provided herewith for the production of multimetal diffusion coatings on metal articles providing prolonged protection against chemical or galvanic corrosion of the surface of the coated article during prolonged exposure to corrosive conditions, and particularly high-saline content marine atmospheres, especially where the protective coating is also subjected to mechanically erosive and abrasive environments, with the multiplicity of coating metals being selected so that the combination thereof provides a coating varying through the thickness thereof from outer surface toward the interface of coating layer and coated article so that the mechanical resistance to chemical corrosion is greatest at the outer surface but decreases as the coating thickness is eroded away, while the components of the coating offering sacrificial or cathodic protection are more concentrated adjacent the coating-article interface so that cathodic protection of the coated articles increases as the coating is removed by abrasion or erosion. As illustrative, the outer coating surface includes a high concentration of metallic components inherently resistant to saline corrosion and/or abrasion, although offering less cathodic protection for the coated article; while inner layers of the coating are rich in metallic components offering high sacrificial or cathodic protection, although less erosion or saline corrosion resistance. |
