Acid zinc pretreatment problem

A. Hello cousin Asghar. The most common sequence is as Efim Ruchman has described, i.e., alkaline degreasing, anodic electrocleaning, rinses, HCl, rinses, zinc plating ...

However, it is not unheard of to have a "double" cleaning sequence, e.g., alkaline degreasing, rinses, HCl pickling, rinses, anodic electrocleaning, rinses, HCl activation, rinses, zinc plating ...

I have not seen this double cleaning sequence used for zinc plating in a long time now, but I suppose it is possible that metal can arrive at a plating shop in such poor condition that it is required. Good luck.

Regards,

A. Hi Asghar, Ted,

We have alkaline anodic electrocleaning after HCl, as the first degreasing is very thorough, the second one makes the hard work in some blind spots of the part.

I think that for cast iron and big parts there will be no difference between this two sequences in performance, but with this double cleaning (degreasing-pickling-degreasing) you have more electrocleaning product consumption because of the acid neutralization.

We use this sequence as a Taiwanese design, we didn't change this because it is very effective in cleaning the part, and our electrocleaning degreasing product consumption is low.

If you do this cleaning and you don't have any problems, I think that way you will have less product consumption. By changing to degreasing-pickling-electrocleaning you will have more consumption but with some tensoactives in your pickling bath you may have better cleaning of your parts.

Hope it's clear enough! Best regards :)