Friday, August 20, 2010

Current Efficiency

Current efficiency on chromium plating as draw on the graph above. Lead anodes, insoluble in chromic acid solution, are almost always used in chromium plating from chromic acid bath. Current velocity is depend on the anode cleaned, if anode have covered with impurities chemical can affected to the current velocity and then effect to the current efficiency itself. After use this lead then formed of lead dioxide that form during use causes by the chromium (III) to be re-oxidized continuously to chromic acid, thereby its concentration at a low value.

We can also use of chemical lead as anode, but if compared with lead alloy as anode, they are much more readily attacked by the solution and causes the formation of excessive amounts of lead chromate sludge. Antimony lead is prefer to be used because of its greater corrosion resistance and strength. Lead-tin-alloys also have high corrosion resistance so that this material also widely used. Other material as anode also recommend by worker of using lead silver alloys, but they are expensive. Combination of those like silver with tin, antimony or both are useful and available in the market.