Summary for pit marks after zinc plating Discussion
Pit marks observed after zinc plating were reported on one lot of DIN rail channels: after basic-bath electroplating, the parts developed chicken-pox-like pits a few days later, and a replated pitted rail pitted again while a fresh rail stayed sound. The answer narrows the likely causes to two possibilities. First, the raw material may be porous H.R. steel, leading to “spotting out” after plating; the responder notes this can be more common in humid monsoon conditions and suggests checking whether any pickled steel entered the line if ED or EDD steel is normally used. Second, the problem may be poor post-treatment after plating, especially failure to neutralize all plating residues before passivation. The advice is that if the base metal is not porous, the plater should review rinsing, neutralizing, and passivation steps carefully.
Q. Dear Sir,
We are manufacturer of DIN rail channels sold in India. We have recently in ONE LOT OF PRODUCTION noticed a particular problem i.e. after the DIN rails were Electro Plated by Basic bath (12 microns out side & 8 micron Inside), we noticed after few days that the material was developing pit marks (Like chicken Pox). We have never faced a similar problem after wards. When we have replated one of the pitted Rail along with a fresh good material, our observation was that the pitted rail gets pit marks again in a few days whereas the other one remains good.
Have you ever faced this kind of problems?. DO you have any remedial measures to prevent such problems. Kindly send your reply.
Regards,
NAGARAJAN IYER
– Baroda, Gujarat, India
2002
A. Dear Mr Iyer,
I am narrowing down a lot of probables to two:
1. Porosity in the raw material, probably H.R.Steel which causes “spotting out” after plating. This is common during the monsoon as the increased humidity accelerates this activity. In other months you may not observe this. If you are using ED or EDD grade steel generally then please investigate if a batch of pickled steel has got into the manufacturing line.
2. Downright bad post-treatment after plating. Ensure the plater has taken steps to neutralize all residues of plating solution before passivation. Shouldn’t normally happen though if the raw material is not porous.
Regards,
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
2002