PLATING ON LEADED STEEL
One type of steel, 12L14, a leaded steel, continually gives us problems with blisters and peeling. Do you have any suggestions as to how we can solve this ongoing problem?
Q. Our shop plates a number of different steels using a zinc cyanide plating bath. One type of steel, 12L14, a leaded steel, continually gives us problems with blisters and peeling. Do you have any suggestions as to how we can solve this ongoing problem? L.F.
A. Leaded steels like 12L14, which contains 0.15 –0.35% lead, are produced to allow enhanced machinability. Essentially, the lead smears on the part surface during the machining process and acts as a lubricant. For platers, the problem with these leaded steels is simple: If the lead is not completely removed from the surface, you will not obtain a satisfactory deposit.
The following cycle should remove the lead on the surface and give you good results:
1) Soak clean to remove oil and grease.
2) Clean anodically at a current density of 90–100 ASF in a strong alkaline cleaner.
3) Dip in an acid such as acetic, fluoboric or glycolic acid. Proprietary acids are also available for this purpose.
Rinse thoroughly between each step.
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