Leaded Steel- Nickel Chrome Plate

Nickel-Chrome Plated 1117-leaded has small black spots on surface. Parts are case hardened and ground before plating. Spots appear to be black with some having plated over but not to the same thickness. Could the be caused by the lead in the steel.

First of three simultaneous responses-- 2001

Leaded steels must be activated with fluoboric acid, sulfamic acid and also available on the market are acids based on citrates to remove smeared lead oxides on the surface before nickel plating. If not, then pitting will result with no plating taking place in those areas. It is most useful on 12l14 alloys. To me, it is imperative a 30 second dip in the above mentioned solutions. I use fluoboric @ 20 %. Most leaded steels react in HCl solutions and is a dead give away it's leaded. No problems since following a pre dip as I mentioned above.

Second of three simultaneous responses--

It could be caused by the lead inclusions if the inclusions were unusually large. This condition can also be caused by the manganese sulfide inclusions that are present in this alloy. The sulfide inclusions can be large, and if they are etched out during preparation for plating can trap etching and plating solutions to cause defects in the coatings.

Third of three simultaneous responses--

For the elimination of the lead caused spots, you have to dip in fluoroboric acid prior to the nickel plating.