What Anodes are Used for Hard Chrome Plating?

What Anodes are Used for Hard Chrome Plating?

Traditional anode for hard chrome plating is made of special lead alloys. Pure lead anodes are attacked by the solution and cause the formation of excessive amounts of lead chromate sludge.

A typical alloy is a lead-tin alloy. When the length and weight of the anode is a problem, anodes are usually lead antimony. Tin-lead anodes have better conductivity and last longer, but antimony-lead anodes are more rigid. Anodes used in high fluoride baths should use the tin-lead alloy, as antimony-lead alloys will have a poor life expectancy and form an abundance of corrosion products. Also, when tank type anodes are used in high fluoride baths, they should be of the solid smooth variety and not hollow or ribbed.

Except for lead alloy anode, iron anodes have occasionally been used, particularly in special instances where greater strength and rigidity are required. Their continued use, however, leads to the accumulation of iron and chromium in the bath. Where iron anodes are used, it is recommended that they be coated with lead whenever feasible. Small platinum wire anodes can also be used for special purposes, such as plating the inside of very small openings, but they too will form chromium in the bath. Copper, nickel, and stainless steel should not be used for chrome plating anodes.

Recently, platinized titanium and niobium anodes have been used more and more in fluoride free hard chrome plating baths, replacing the common lead and lead alloy anodes. This platinized titanium anode can increased throughput with reduced plating times. The Anode geometry remains constant to obtain optimized plating results, it has long operating life, very low maintenance, and can increased bath life.  
 
For most plating situations, the anodes are usually shorter than the cathodes. This tends to decrease the excess current that would otherwise flow to the work at the bottom of the rack. The bottom of each anode should be at least 6" above the bottom of the plating tank. When the part contains sharp, narrow recesses, such as grooves, a reduction of the anode distance may help to increase the thickness of the deposit at the bottom of the grooves. However, some parts with sharp-cornered grooves, bosses, and undercuts cannot be uniformly covered unless conforming or auxiliary anodes are used.