Spot Weld on Zinc Plated parts

By rclAN Date 01-20-2003 15:16

I am trying to convince a colleague that we can save some money by having parts zinc plated (zinc dichromate). He keeps on coming back with things to push this project to the side. First he tried to tell me that the a spot weld wouldn't hold, then he said the zinc wouldn't take a powdercoat. I have proved him wrong on both. Now the latest and greatest is the hazard spot welding a zinc plated part would have on the operator. Can anyone tell me if welding zinc plated parts would give off hazardous fumes? This coating is 0.0025 inches thick and requires only a small spot weld. If so, wouldn't a simple vacuum installed above the welding table work to reduce the fumes?

By jwright650 (*****)

Date 01-20-2003 15:27

rclAN,
We use a disposable respirator 3M part number 8514 N95 that seams to help our guys if they have alot of welding to do on galv'd materials. Our shop has really wide open bays and we have to have alot of this material being welded before it becomes a problem. Some people seem to tolerate it better than others. I feel like the stuff builds up in your system over time and a respirator will help filter out alot of that yellow-green smoke that makes you feel so yucky.
Hope this helps,
John Wright

By dee

Date 01-20-2003 22:57

Although I cant help much, the post got my attention.

First, I was under the (quite possibly incorrect) impression chromates were under pressure to be subsitituted with alternatives having less environmental impact. I thought they were on some kind of phase-out schedule, which might be European, along with Pb and other industrial toxins. I would protect (ventilate) and be concerned with the chromium if I had no choice of alternative... the Zn is obvious but toxicity issues with Zn do not bother me nearly as much. As for this "list" it DOES exist; I am not sure whats on it.

I'm curious about what you are presently using that this new process is intended to provide economy over, and how the theoretical-based objections were determined to be invalid.

I've never known John Wright to be wrong (no pun) but I would be concerned about Zn contamination cracking & failures in an inverse proportion to the size of the weld, but in practice and real terms I have no idea how much contamination might be permissible.

In any case, the real point is heads up about the Cr, not the Zn.

Regards,
d

By jwright650 (*****)

Date 01-21-2003 20:52

Although I did not mention the issues that "Dee" brought up, He has a couple of very valid points. The Zn should be removed from the critical weldments prior to welding. The Zn mixes with the weld metal jepordizing it's integrity. I'm glad that "Dee" was paying attention and helped me out of that one. I don't want to mis-lead anyone.
John Wright
Hey Dee, no pun taken