Abstract
The effects of phosphorus content on the structure and corrosion resistance of electrodeposited Co-P alloys have been investigated. X-ray diffraction revealed that alloys containing less than 4% phosphorus are super-saturated solid solution, the deposits containing 5-15% phosphorus are amorphous, while more than 16% phosphorus alloys show the structures of Co2P crystal, intermetallic compound. The corrosion resistance of alloys with different P content was investigated by anodic polarization. The amorphous alloys containing more than 10% of P showed excellent corrosion resistance in 1 N HCl and 3.5% NaCl solutions. The AES profile revealed that P was condensed on the surface of alloys. However, it polarized to more anodic potential, the phosphate was formed and the corrosion resistance become poor. In alkaline medium, corrosion resistance was improved with increasing content of P. Thus, alloys containing more than 10% of P were self-passivated in 1 N NaOH solution.
