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Rj_
Tinkerer
Username: Rj_
Post Number: 20
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 19, 2007 - 04:55 pm: | 
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I'm half-way through restoring a Sanderson and due to the vintage imperial sizes of the parts which have mostly corroded, I've realised that it makes more sense to strip off the brass coating of corroded gears and brass turnwheel knobs and plate electrolytically. The alternative is trying to source solitary screws and metal parts, one at a time, which is extremely inefficient.
Has anyone used either the closed contact brush technique? I wonder if this is as consistent and uniform in the plating process as the electrolyte dip technique.
Although I don't have a fume cupboard, I use a centrifugal industry grade chemical filter in the workshop.
I would appreciate any advice or signposts if anyone has experience of this.
Kind regards,
RJ |
Gez
Tinkerer
Username: Gez
Post Number: 3
Registered: 09-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 20, 2007 - 03:28 pm: |
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A specialist electroplating firm is one way, alternatively you could try this little book; 'Electroplating by J Poyner,ISBN 0-85242-862-6. It gives good details of proper electroplating with copper and nickel without having to use dangerous cyanides. Chrome plating isn't covered. Well worth a read. |
Jon_goodman
Tinkerer
Username: Jon_goodman
Post Number: 7
Registered: 05-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 20, 2007 - 07:08 pm: |
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Yes...but plating chrome is not really anything to be tried at home. The gimmicky "plate with your car battery" gizmos will be less likely to apply chromium than a frying pan. I think you might be best advised to plate with rhodium (a hard white metal which sort of mimics chrome or polished stainless, but is pretty doggone expensive). You can plate it with a smooth 12v DC power supply (no AC in the output at all). If you want to try chrome plating at home, you're about 25 years too late. You can't buy the necessary stuff without an EPA permit and you probably wouldn't want to handle it, anyway. There is an outfit in Davie, Florida who used to sell small (1 ounce) bottles of Rhodium plating solution, but be prepared to spend about $50 or so. I don't know any platers who will take on small jobs for less than about twice that. Especially screws and things. Those drive them nuts. Good luck!
Jon |
Jon_goodman
Tinkerer
Username: Jon_goodman
Post Number: 10
Registered: 05-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 21, 2007 - 06:23 pm: |
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I checked with the folks in Davie (Samson Technologies) and rhodium is $55 for a 1 oz bottle plus shipping. Yowtch!
Jon |
Rj_
Tinkerer
Username: Rj_
Post Number: 21
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 22, 2007 - 04:54 am: |
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Hi there,
thanks for all the advice. Gez - I'll order Poyner's book. It sounds like it's the kind of primer I'm looking for. I'm not keen to outsource electroplating such small items to a specialist is worthwhile: most offer either chroming services, and expect a substantial car sized bumper, rather than miniscule wood screw for their order. Updating and revising my knowledge of chemistry, I believe it is possible to electroplate without producing anymore cyanides (the selenium toner does enough of that 
Jon - I think the reason why standard home DIY chroming kits fail is because chromed metal does not accept chroming and tends to slide off. By generating a power current of around 1.0 Ampere/square inch, I think I can resolve this issue once the the metal is stripped back to steel or nickel using Hydrochloric Acid (1 part to 2 parts water) and/or chemically stripped in a suitable electrolyte bath before the plating process is attempted.
What is an EPA permit? I think regulations in England may be substantially different from the States in this respect.
The Rhodium "copy-chrome" is certainly what I had in mind - I think there are specialist kits in England which offer either 'brush' plating using an AC-DC rectifier with two crocodile clip contacts and a wand, or alternatively, a dip bath technique which is more substantial in its layer of the chrome.
One of the advantages of a brassing solution instead of chrome is that it can be stressed and oxidised or antiqued, in order to restore the vintage look of the original brass, without the crumbling rust. I see it's possible to blacken brass for a very striking finish.
$55/1 oz is expensive. I've hunted around some chemical stores in England - I think I can find the appropriate brassing solutions and copy-chrome solutions for less than that.
Kind regards,
RJ |
Jon_goodman
Tinkerer
Username: Jon_goodman
Post Number: 12
Registered: 05-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 22, 2007 - 08:03 pm: |
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Hello, RJ.
Plating chromium is a three part process...first copper, then nickel then chrome. Unfortunately the final plating uses chemicals like cyanide, and I can not imagine you could still purchase that in the UK without strict controls. It is poison of the worst type. To apply real chrome otherwise is going to be fruitless. You can not plate chrome onto existing chrome, no matter what anybody says. That is like trying to stack marbles. Rhodium can be safely electroplated with a sacrificial anode system (you mentioned the "wand"...that would be a sacrificial anode and the "swab" that covers it would host the electrolyte) and a good DC power supply, but be careful...actual bonafide rhodium is very expensive, no matter where you get it. Be sure who you're dealing with. Some of the imitation chrome will turn odd colors in a matter of weeks.
Jon |
Glenn
Tinkerer
Username: Glenn
Post Number: 177
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 23, 2007 - 09:17 am: |
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The simplest plating method for home use is 'Electroless Nickel'. This is basically a two part solution which you maintain at a constant temperature whilst the parts are immersed. The solution temperature and time of immersion controls the plating thickness. The solution will even plate plastics with the correct treatment. The as plated finish can be polished, ground down - reclaiming worn parts or otherwise machined.
I use a product produced by Cannings and in the days when the UK Government allowed the private individual to own and shoot handguns, I refinished a number of automatics which had a hard competitive life. I only mention this to indicate how versatile and hard-wearing this plating method is. My equipment is very basic - small laboratory hotplate, accurate thermometer and a collection of large laboratory beakers. Because the amounts of solution used are so small, I follow a use once and throw away policy. This saves having to check and replenish the solution. |
Rj_
Tinkerer
Username: Rj_
Post Number: 24
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 25, 2007 - 09:55 am: |
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I've found one supplier in Europe:
http://www.caswelleurope.co.uk/Kits.htm
Their Technical Department is very helpful. Unfortunately the prioprietor is away until the end of this month so I won't be able to draw on the plating work until then.
Here is a link to the Caswell version of 'copy chrome':
http://www.caswelleurope.co.uk/copycrom.htm
And brass plating:
http://www.caswelleurope.co.uk/brasplat.htm
Glenn - The Cannings Plating expertise still featured in modern Chemistry textbooks primers by Wiley publishers ;) |
