The authoritative public forum
  for Metal Finishing since 1989
-----

Zinc plating issue on sheet metal welded part

May 20, 2009

I have sheet metal shelf which consists of 5 rectangular compartments in series. Each of these compartments is spotwelded at the 4 corners to the adjacent compartment. This shelf then gets electroplated with zinc with clear chromate finish after the welding. It is critical to plate the shelf after the welding so that the spot weld areas also get plated. Also, both the inside and outside surfaces of the compartments must be uniformly plated. Each rect. compartment is 3.4" X 1.7" and the material is 22 GA (0.031" thickness) cold rolled sheet steel.

Our plater in China is complaining that they cannot do good quality zinc plating without punching a series of rect. holes on top and bottom of each compartment. Apparently they require these holes for drying the plating solution. Adding these holes is not acceptable because of strength issue.
1. Can they use forced convection or a warm oven to dry? Is there a recommended procedure for drying?
2. How can they ensure plating inside the compartments? Adding electrodes inside...?
3. What is the recommended process flow for Zinc plating with clear chromate so that I can ask our Plater in China to follow this.

Sandeep Yadav
product designer - Burnaby, BC, Canada

Hi, Sandeep, and welcome. We're always happy to give anyone a quick tip. Worldwide camaraderie among peers is what this site is about. If your Chinese plater signs on here, I'll try to answer his specific questions and I'm sure others will too. But you're not asking struggling platers in America, Europe, Australia, and India to simply share a quick tip with a new friend from China, but to assist in a one-sided transfer of technology to China. I don't think it's xenophobia when people don't feel like doing that :-)

My suggestion would be to go to one of the international suppliers of zinc plating and chromate process chemistries, who offer their products both in Canada and China, and ask them if they will sit down with you to work this out. Best of luck!

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 21, 2009

---

August 13, 2009

Dear Sir:
If you want to get good surface treatment on your cabinet,you have to request your job plater pay more attention to following points:
1.Alkaline zinc solution is the most suitable type for this kind of workpiece, on compare with acid zinc solution, alkaline zinc has more better throwing power, so you can get more uniform Zn deposit inside cabinet.
2.Auxiliary anode is necessary for inside Zn deposit if punch hole is impossible.
3.The job plater have to find a flexible rack tool to loading workpiece and dump out solution.

Wang Gang
ATOTECH - Qingdao,Shandong province,China