Particles underneath the e-coat: Problems & Solutions

A. Dear Alfred,

Maybe your operating voltage is too high or phosphating is too thick. Try working with both these parameters one at a time and see which works.

A. 85 volts is not high in my experience; however you might want to increase time up to 3 minutes with the same voltage and check for results.

Are you sure your phosphating is done really well, no rough grains, no sludge sticking to the edges, phosphating solution filtered crystal clean, fresh activation bath every second or third day?

A. Hi Alfred. Sorry that there is perhaps a bit of a language problem, but nobody said the "phosphating high". Someone did suggest that the phosphating might be too thick or heavy, as well as suggesting that the voltage might be too high -- but the suggestion of the voltage possibly being too high was before you told us what it was :-)

What are you doing for pretreatment, i.e., what do you do to the parts before they enter the CED tank? I think you need to spend some time describing what you are doing, perhaps send photographs, because 3-1/2 months later we're still not quite understanding your questions :-(

Regards,

A. Hi Alfred. I think you're repeating the question without giving us additional data to try to help you.

Maybe you feel that this problem has just one possible cause and that by describing one incidence of it we should lead you to that single cause, but it usually doesn't work that way. Every cough isn't lung cancer, nor every belly ache appendicitis ... there is more than one possible cause for roughness along an edge.

We don't know whether the article is made of steel or aluminum (or something else).

We don't know whether you chromate it or phosphate it, or something else.
We don't know if it happens on every part, or just on one part out of a hundred.
We don't know if it's a new problem and you used to successfully e-coat, or whether you've never yet achieved success.
We don't know if it happens on top edges, bottom edges, or vertical edges, or everywhere on the part; we don't know if it happens on the topmost row of parts on the rack or the bottommost, or everywhere.
Are you sure that there are no burrs before the parts enters the e-coat tank? Thanks!

Good luck.

A. Hi again, Alfred. If some models come out fine, it sounds very unlikely that there is a chemistry problem in your CED tank, assuming those other parts are stainless steel as well. I suspect that the other models which coat properly do not have quite the same sharp edge. Even the vertical edge of this part may be different if it doesn't have the problem. Unfortunately, we're not helping you much.

What process do you do immediately before electrocoating? Is it zinc phosphatization? Phosphating of stainless steel is problematic. I would suggest you try blasting a couple of samples before CED coating and tell us what happens at the edge in this case. Good luck.