Improvement of the corrosion behavior of electrodeposited CoFeCu thin films

The limited range of Cu that must be added to achieve reasonable magnetic and corrosion properties during the deposition of CoFeCu alloy-based thin films is a stringent control issue in manufacturing. The use of limited amount of phosphorus added in the bath to confer better corrosion properties on the thin film is considered in this work. Potentiodynamic polarization technique in 2.5 wt.% NaCl solution was used to study the corrosion properties of electrochemically deposited CoFeCu thin films that contained varying amounts of phosphorus. The results indicate that the addition of limited amount of phosphorus improves the passivity of the CoFeCu thin film. The range of the amount of phosphorus required to be added in the alloy for best corrosion properties was defined. For the bath chemistry and composition studied, the level of corrosion resistance improvement was found to be limited to a phosphorus-alloy content of between 3.0 and 5.3 at. wt.%. (above this phosphorus-alloy content, a fully amorphous alloy is thought to be deposited).