The effect of the pH on the composition and properties of Co-W alloys manufactured from gluconate electrolyte

Effect of P codeposition on the structure and microhardness of Co–W coatings electrodeposited from gluconate bath

“…Co–W coatings deposited by using DC and PC methods show 46.2 and 49.5 wt.% W, respectively, wherein pulse plated coatings contain higher amounts of tungsten. Weston et al have reported similar composition, while Bobanova et al have reported a lower amount of tungsten at similar pH and current density. Addition of 2 g l −1 NaH 2 PO 2 to the electrolyte has facilitated the codeposition of P with Co and W. Drastic increase in cobalt and decrease in tungsten content in the deposit are observed after the addition of hypophosphite into the electrolyte in both electrodeposition modes.…”

“…Recently, electrodeposited cobalt and its alloy coatings, especially Co–W and Co–P coatings, have been studied extensively for their amorphous nature, increased hardness, higher thermal stability and enhanced wear and corrosion resistance. These coatings are also considered as potential replacement for conventional hard chromium which poses health and environmental threat.…”

“…But, in recent times, owing to their nontoxic nature and easy availability, usage of gluconate as a complexing agent has gained increased attention in electro as well as electroless deposition methods. Co–W coatings obtained from gluconate baths under various conditions have been observed to demonstrate high hardness , significant corrosion resistance , wear resistance and good thermal stability with glass‐forming ability (GFA) , making them a strong and potential contender for the replacement for conventional hard chromium. However, the effect of alloying non‐metal like phosphorous to improve the properties of cobalt‐based alloys is a topic of recurring interest.…”

“…Most of the Co–W–P and other ternary alloy coatings have been obtained from citrate baths while recent investigations on the codepositon of P and W individually with cobalt from gluconate bath have also led to promising results . Weston et al have used gluconate bath for the electrodeposition of wear and corrosion resistant Co–W alloys and established a relationship between the bath composition and the alloy properties .…”