The authoritative public forum
  for Metal Finishing since 1989
  

  -----

How to do Chrome Plating of a Closed Square Tube

please can anyone help. I have manufactured a bed frame plus head and foot ends out square tube,25x25x1,6. I now wish to have it chromed. it has been totally welded all round. I have now been informed that I have to drill 5 mm holes in either end of the tubes. as this is a cold process I cannot see the reasoning behind this. PLEASE HELP.

Steve laubscher
- South Africa
2000

---

2000

Hi, Steve. It is unfortunate that you didn't have a chance to discuss this with the plater before the fabrication was completed, but if I ran the shop I'm afraid that I would probably have exactly the same reservations.

There are 4 issues here. First, the process is not really 'cold'; the plating operations will run about 140 °F and the cleaning process about 180, maybe even 200. There is somewhat of a safety issue; it's unlikely such a closed tube would actually explode in a plating process, but workers in galvanizing plants (hot process) have been killed by such bombs, and if the part were to mistakenly find itself in a black oxide line, with leakage of water into it, it could certainly blow up the tank.

Second, if your welds leak even a little, just pinholes, that tubing could become full of solutions that will be dragged into subsequent tanks, contaminating them.

Third, imagine that that leak happened in the chrome plating tank and the plater ended up shipping you a tube with a quart or so of toxic hexavalent chromic acid (hexavalent) chrome in it?

I sympathize with your pride in workmanship, but your part is unfortunately a serious problem. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey