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Zinc metal build up in plating solution

2004

We have an automatic barrel- acid chloride zinc plating line.Our zinc plating solution is of 2000 USG capacity.We maintain total chloride at 145 g/l and boric acid at 30 g/l.We used to have our metal content at 35 to 37 g/l.But for past few weeks it is at 47 g/l.Ideally we want to maintain it at 30 g/l.( cloud point is at 150 F) Our existing options are to reduce anode baskets without affecting surface area of anodes and / or remove the baskets on weekend.

And I studied in literature about use magnesium and aluminium alloys of zinc which reduces the metal build up.

My questions on that are :

Is it commonly used and is it proved to be successful?

Does it affect the current efficiency and properties of the deposit?

Is the corrosion resistance of the deposit same

Or is there a still better alternative.

Thanks

Venkat Raja
- Kitchener, Ontario, Canada

Venkat,

We experienced the same problem on our rack acid chloride zinc line (rising [Zn]). I switched to a different brightener system that was compatible at higher pH's (~5.5-6.0). This seemed to help. I also switched from a boric acid/KCl bath to an ammonium chloride/potassium chloride system. It was a quick and easy solution in my application.

Hope this helps.

Trent Kaufman
electroplater - Galva, Illinois
2004

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Hi Trent,

Thanks for your response. As mentioned in your reply I do have an option of going for a different brightener system which doesn't oil out in high chloride concentration. But I am still wondering whether there are any other options to prevent metal buildup.

Venkat Raja
- Kitchener, Ontario, Canada
2004