Electroplating old parts - DIY Zinc Chromate and Parkerising
As part of some of the work I'm doing now that I have the body off my G, I'm putting together a plan to clean up and re- zinc plate a whole bunch of stuff. I thought it might be interesting for other members if I documented some of it here.
The 3 processes I am going to try are:
Zinc electroplating with yellow Chromate finish (Olive drab and black are also options)Nickel with copper layered - to allow filling of pitting on a couple of bracketsParkerising - manganese oxide black which I'm going to use on some larger steel parts.Starting Out
My starting point has been one of the Zinc plating kits from Caswell Europe, which was a kind of expensive place to start since many all of the precursor chemicals are available more cheaply. On the other hand, its been 25 years since I did any electrochemistry and the guy who owns/ runs it in the UK is very friendly and helpful (he's called 'Jeep') .. definitely worth the extra cost of buying the initial kit if only because safety is top of their agenda and being able to phone someone up to ask 'should it be making this green gas?' (answer: NO!) is well worth it.
The good news is that for most of the plating I want to do (and I think will be of most interest here) - which is essentially Zinc with a Chromate oxide applied, none of the chemicals involved are super toxic in the way that many plating materials are (Cyanides and Chromic acid for example).
That's not to say you want to screw around with them either of course. Most of the processes involve strong acids at some point which should be treated with respect. Other chemicals are poisonous but not to the extent that they can't be handled using sensible precautions.
Electroplating processes also give rise gasses (hydrogen ususally, but carelessness with Hydrochloric acid can prodce Chlorine and Nitric with oxides will give off NO2 which is also toxic). Good ventillation, gloves/ googles/ no eating/ smoking are the order of the day. If you have never done any chemistry (the important part being the materials handling) then I'd guess this is still doable, but you'll want to take extra care and advice around what and how to do what (example: you generally never add water to acid, rather acid to water to avoid strong reactions spitting back at you)
The process though (and I'm only just starting out with it) is quite simple and from what I've seen the results people obtain can be as good as commercial OEM - in some cases better because you are in control of how thick the plating is.
It is the old thing of you get out what you put in - super corroded parts will still look pitted no matter how thick the plating (though you can use techniques like copper plate and solder filling to fix this).
Cost wise, a basic Zinc/ yellow Chromate kit will run to about £150, so there's obviously a trade-off point between DIY and outsourcing it. In my case though I'd got tons of parts I could do and besides which I really enjoyed chemistry so this is a bit of fun too.
Anway, if there is interest (please let me know below) then I'll start writing stuff up as I go and post commentary here with pics on my Flickr account.
Hello fcp,
Thank you for posting this thread. I have only just read it despite that, it has been on the site for a little while.
Any how, I was going to do research on cleaning and treating wheel bolts, as these seem to rust out relatively quickly and to me, seem to be unsitely. Given, the topic showed very little interest on the forum, I decided against writing up and spending time to research the topic further.
It would be interesting to see how you tackle this issue, should it be on your agenda. As far a my limited knowledge on the topic stands, manganese phosphate treating the wheel bolts, is the best process available
process to treat the bolts. But, I do not like the finish, it is black. I understand that, Land Rover or the MoD Land Rovers use this process to treat their wheel bolts.
Chrome plating is the more acceptable finish but does not last well, it is prone to peeling or flaking and the has tendency for rust and can blister from underneath the plating; to an extent sometimes, the wheel socket has to bashed on the nut or bolt, in order to remove it.
Keeping an eye on this topic.
Regards,
Keep up a report please.. I have looked at these kits (even for work as no one will spot plate chrome of the size of lumps we play with). Never actually ran the zinc or chrome plant but used to spend 1-2 hours a day monitoring the flow of brake parts through them in a previous life so have a good idea what goes on.
Are you going to electrolytically derust as well? Another of those toys I intend to get set up one day..
No, i'm derusting with Hydrochloric acid (HCL) at around 36% solution (12 molar approx). You can buy this concentration often as 'Brick Cleaner' from trade outlets.
This is very efficient at cleaning the rust away back to base steel forming Iron (II) Chloride and water (2HCl + FeO >> FeCl2 + H2O). The hydrochloric acid will also eventually react with the steel if youleave it in too long, but we are talking hours at room temperature.
Once you have cleaned it though, you havce got to move to plate it almost instantly as otherwise the part will 'flash rust' - before your eyes!
For heavily pitted parts I'm either:
Chucking them away and buying new (not worth the effort for a £5 bracket often)..
.. or trying a 3 stage process to nickel plate, followed by copper (you can't easily/ safely copper plate steel directly DIY), filling the pits with Solder and the Zinc Chromate over the top. That should bring them back to new and they'll never corrode again (theory!)
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Hi Rakesh,
Cool, so I'll take care to document stuff as I go along and detail it here.
Parkerisng of steel (manganese or Iron phosphating) is quite durable I think, though strictly speaking the corrosion protection comes from the appication of oil to the surface of the finish once it is done (the textured finish takes the oil up and seals against oxidation. It is used a lot as a very durable, matt firearm finish (I think it was the USA that first exploited parkerising extensively during WW2) but as you say for wheel bolts you either love or hate it.
Parkerising is one of the things I am going to try (I might even do the wheelbolts)
For the other options, I suspect that a hard chrome finish would actually be quite close to what you want (used in engineering to finish surfaces against wear I think. From the ASM Metals Handbook #5
HARD CHROMIUM PLATING is produced by electrodeposition from a solution containing chromic acid (CrO3) and a catalytic anion in proper proportion. The metal so produced is extremely hard and corrosion resistant. The process is used for applications where excellent wear and/or corrosion resistance is required. This includes products such as piston rings, shock absorbers, struts, brake pistons, engine valve stems, cylinder liners, and hydraulic rods.