Zinc brightner consumption

[pdeinc]

My very first part came out far better than expected - uniform coverage, nice bright finish, everything I'd hoped it'd be. Subsequent parts are less so. After about 3 parts, all about 12 sq in, I added another 3 1/2 tsp of brightner per the manual. Altho the next piece was somewhat better, following pieces are not. Is the brightner really consumed that fast?

All parts so far are what I would call exceptionally clean - bead blast, acid washed, detergent washed, SB de-greaser bathed. So I don't think the solution would be considered contanminated. I'm using compressed air run thru a filter into the tank for agitation. Coating still appears to be depositing as expected, just not 'bright'. I can polish them with a little Mother's but then I get a 'polished' finish that looks more like chrome than bright zinc.

Anyone else had similar experience?

FWIW - Two gallon system using supplied power module. Parts are steel with original zinc finish before bead blasting.

[dadkar2]

I had this problem with the nickel and found I needed to do a few things to my process:

1. Went to a professional grade cleaner (uses NaOH so it needs to be handled VERY carefully)

2. Added a two-stage distilled water rinse after the cleaner, and also after the acid pickle. This assures that the pH of the plating solution isn't altered by drag-in. Two-stage means you have two separate distilled water buckets. You rinse in #1, then rinse in #2. After a few parts, dump #1, rotate #2 to #1, and refill the #2 with fresh distilled water. The idea is to always keep that final rinse as clean and close to neutral pH as possible.

After doing these things, the nickel lasted much longer. However, after 3 months it became troublesome again. I contacted the original manufacturer of the nickel solution and it turns out there was an improved brightener available. Now the nickel is flawless and a tank lasts a little over 6 months of fairly heavy use.

I have a feeling that getting much more than 6 months out of a small plating bath without a full-time chemist is going to be tough. So at that point I take the spent solution to the household hazardous waste reclamation service and start over. Much easier than trying to salvage a bad tank. And, 2 gallons every 6 months is definitely well under CESQG class!

After you implement the rinse, talk to Caswell about the brightener consumption. There may be better products that haven't been announced.

Kind regards,
Ken

[pdeinc]

I'm not near the ingredients at present but I though the cleaner was NaOH. I wasn't aware that the 'drag-in' might have as much of an undesireable effect as you indicate. I was just rinsing by a spray bottle of distilled water while the piece was suspended over the degreasing solution.

Ill talk to Caswell in the morning and change my rinse procedure before the next batch. Thanks so much for your input.

regards,
Ken (good name, huh?)

[dadkar2]

I don't know how well the spray bottle works, but I can say I had been using a single dip rinse and it wasn't sufficient.

Kind regards,
Ken