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-----Cleaning of Capscrews
1999
Hi Guys,
First time for me posting a question, hope someone can help me?
I recently started my own plating company and I am finding difficulty in the cleaning of some products.I previously worked for a large plating company and never came across the types of items which I am asked to plate now.
The items which cause particular trouble are as follows:-
- 1. Capscrews, Button head screws 12.9 , 10.9 grade
- 2. Csk soc screws 12.9 10.9 grade
The process I use now is as follows:-
- 1. hot soak clean
- 2. electrocleaner
- 3. hydrochloric acid 50%
- 4. water rinse x 2 5. electroplate
I find that the items do not clean correctly and I find myself having to strip and replate on a regular basis, which messes up my production pattern.I currently use a cyanide zinc solution and also alkaline non cyanide, I find that the cyanide plates better over the dirt left on the capscrews than the alkaline non cyanide process.
Any help on how to properly clean and plate these items first time would be greatly welcomed. Another problem is drying of rack plated items, we currently plate a lot of 1 metre threaded bars and also a lot of 1/2 metre tubing which have to be zinc plated with a clear passivation.The problem which occurs on these items means I can't get a consistent blue/clear finish on these items.I seem to continually get water marks on my items.I currently dry these parts in a tank with a gas burner underneath.
How can I stop these marks from appearing on my parts?
We use the alkaline non cyanide zinc for rack plating with a nitric acid dip before passivation.
Please can someone help me
regards George
- United Kingdom
1999
Hi George,
Welcome to the wonderful world of owning a startup plating shop.
These are not simple parts to get clean. Probably the simplest is after the acid rinse, go back into the electrolytic cleaner.
Next, I would try a periodic reverse and tweak the bath to accommodate the change. A little higher temp and a slightly stronger cleaner might help. I would consider using 40% acid.
You might have to wet blast them to get them clean enough. cyanide is a wonderful cleaner, even in a plating bath. Very forgiving relative to a non-cyanide one.
Try heating your final rinse to 130-140F and use RO or DI water for a final rinse. You might even have to go to a 10%
isopropyl alcohol
⇦ on
eBay or
Amazon [affil link] to further knock down the spotting.
Use air rather than heat to dry your parts,as it will blow off most of the water. Warm air works better than cold.
- Navarre, Florida
Ultrasonic cleaning is a good possibility if you can afford it.
James Watts- Navarre, Florida
1999
1999
Hi George , Welcome to plating , its a hard life but rewarding !
George , I would think that you should be more worried about Hydrogen embrittlement with Cap screws , I have been involved with a company producing them here in Aust. and they are pretty keen that they are :-
- Never stripped and replated
- Not plated in Cyanide solutions
As a matter of fact they specify all their hardened products be Mechanically plated ! However , I would not go that far, I would recommend that you look at Chloride Zinc , it's a lot easier to plate on hardened & Carbonitrided surfaces than Cyanide Zinc , all the OEM fastener manufacturers that I know of that Zinc plate in house do so from Chloride Zinc , it is quicker , less chance of HE , and plates first time every time on hardened fasteners & no Cyanide to treat ! However to your cleaning problem I would recommend you install after your 50% Acid ( which I hope is inhibited ) and its rinses a Heavy Duty Alkaline deruster , that operates about 60 °C and at 25 amps / square foot anodically , you would need to have it operate for about 1--> 2 minutes per load . You will also need to modify your waste treatment system to use lime as the neutralizing agent as these Alkaline derusters / Smut removers are highly chelated . best regards
John Tenison - Woods
- Victoria Australia
I ran a job similar to this years back , a few different ways, barrel and rack.... we used a real nasty cleaner , cyanide based with a deruster , on a periodic reverse unit , clean / rinse / acid / rinse this did an excellent job on mil spec screws that were real nasty...... hope this helps
Ron Landretteplating equipment supplier - Bristol, Connecticut
1999
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