Home DIY ZINC Plating

[cully]

DIY Zinc Plating for small piece's, Nuts and Bolts

following on from Ben's restoration and his bought Bright zinc plating kit
i thought id have a go on the cheap!

    If you have rusty parts and have not read the thread on Electrolisis cleaning go here and start reading as this can be used to clean the parts you want to Plate with Zinc.
http://306oc.co.uk/forum/showthread.php?tid=22295

    One problem with electrolytic de-rusting is that the part comes out of the de-rusting bucket with no protective oxide layer, so you must immediately do something to passivate or seal the exposed metal or it will start rusting before your eyes. Painting works great on larger parts, but not so well on nuts and bolts, and certainly not very well on threads. this is where I decided to try home-brew zinc plating.

    As it turns out, zinc plating is pretty easy to do at home, with easy to obtain materials that are not particularly dangerous.


    If you want to give it a try, here's what you will need...



    1) A supply of nearly pure zinc metal. I bought I bought mine off of ebay shipped from china.

    2) A low voltage power supply, i have used an old 5v DC mobile phone charger cut the plug off and fit crocadile clips to the leads you will need to know the + - polarity.

    3) Distilled Vinegar from Tesco's about 50p for 500ml. Vinegar is actually a mild solution of acetic acid and is what slowly dissolves the zinc metal into solution.

    4) Epsom Salt from the Tescos bath soap isle, I got mine from thesoapkitchen.co.uk £1.25 for 500g . Epsom salt is Magnesium Sulfate and is the conductive "electrolyte" of the plating solution.

    5) Sugar from Tescos. Sugar is the "Brightener" of the plating solution. It actually interferes with the formation of zinc crystals, causing many smaller crystals to form on the surface instead of fewer larger crystals, thereby improving a frosty looking surface to a smoother more reflective one.

    6) You will also need clean plastic containers to mix and store the plating solution and do the actual plating.

    The plating solution recipe (which you can scale up or down as you like):
    1 liter of vinegar (5%)
    100 grams Epsom Salt
    120 grams sugar
    1 zinc strip

    Add the Epsom Salt and sugar to room temperature vinegar and stir until dissolved. Add the zinc strip and leave lightly covered for 24 hours.

    You may not see any bubbling for the first few hours, but by the end of the first day you should see small bubbles coming off the zinc pieces. This is the zinc metal being converted to soluble zinc acetate while liberating hydrogen gas. Don't tightly cap the solution or the pressure from the hydrogen gas will build up and the container may Leak. The longer you wait for the zinc to dissolve, the faster the plating will build up when you start your first run. Once the run starts, you are actually dissolving zinc off the anode at the same rate you are plating zinc onto the cathode, so the zinc in solution should not get depleted.

    To actually plate something, make an anode (+ terminal) of zinc metal,I used the strip and lined the edge of the container.
attach the cathode (- terminal) to the part you want zinc plated.
The submerged area of the anode should be a little larger than the area of the part being plated.


    
If your solution has a sufficient amount of dissolved zinc acetate then you will see the part start to turn zinc colored almost immediately.

  apparently if you adjust the voltage/current you can get different or better finishes
at present im only experimenting and want a protective coat layer of zinc

Voltage current theory...

    The voltage should be adjusted for about 65 mA (milli-Amps) per square inch of part being plated. Of course most of us do not have a milli-ammeter so some experimentation should be expected. The goal is to try different amounts of current and select the setting that gives the nicest looking coating. If the voltage is too high the edges of the part will look uneven, or have a burned look. If the voltage is too low the plating run will take too long and the finish may be more frosted or dull looking. If the voltage is set correctly, only a very slight amount of bubbling will occur. Violent bubbling means the voltage is too high.



    After 10 minutes or so remove the part and give it a light rub with a ScotchBright pad to shine it up. If the plating looks too thin you can stick it back into the solution for another run.




    It is preferable to do a sequence of several short (10 - 15 minute) runs with a rub between each, than to do one long continuous run in the plating solution.

    The most important preparation step is cleaning the part. The plating will not stick to fingerprint oil, dirt, or any contamination. Most commercial plating shops have very thorough cleaning steps with a final acid etch bath just before the plating run. Scrub the part with detergent, rinse well, and wear gloves to keep the part clean. This is apparently the most common cause of peeling in DIY endeavors.

Acid etch cleaning...
i found this out by mistake....
if you run the Electrolisis bath with the + on the work piece this will clean the work piece
be warned it will erode the part away but short bursts in the bath will bring it up clean

If you were to use this as part of the cleaning process i would not use zinc as a cathode use mild steel as the zinc will get very contaminated and if used later to plate it will contaminate your Electrolisis bath liquour

finished parts im playing with at the moment



there is a lot of copy paste in this guide as ive found info from other sources
but i have got it to work and am able to coat metal items with zinc

[Eeyore]

great guide. thanks cully. Im sure many of us will be using this soon!

[Toms306]

Might be a daft question but why is your zinc silver and Bens is Gold? Can't forge pound coins with silver coloured plating...

[cully]

Might be a daft question but why is your zinc silver and Bens is Gold?  Can't forge pound coins with silver coloured plating...

The normal zinc-plated coating is dull gray in colour

Bens use's an extra process which gives the coating its colour, also Ben controls the voltage and current more closley to give it some shine

mine is the raw zinc coating with no further process using stuff that is cheeply available

[Toms306]

Ah I see.

[Rippthrough]

Yellow dichromate conversion layer over the zinc that turns it gold and gives it much more corrosion resistance.

[welshpug]

I know using SS in electrolysis is a bad idea due to the gases created, is that the case for this as well?

[Rippthrough]

Hydrogen usually. Don't smoke nearby...

[Dum-Dum]

Great guide Cully


Maybe needs a note about the Hydrogen created otherwise we are gonna have people with garages doing Hindenburg impersonations.

[cully]

DONT USE STAINLESS STEEL AS ELECTRODES!

Why you should not use stainless steel electrodes for electrolysis
Many people using the electrolysis method for rust reduction swear by stainless steel, stating (incorrectly) that it's not consumed, stays clean and seems safe.
Stainless steel is indeed consumed when used in the electrolysis process, although slowly. The main problem with using it is the hazardous waste it produces. Stainless steel contains chromium. The electrodes, and thus the chromium is consumed, and you end up with poisonous chromates in your electrolyte. Dumping these on the ground or down the drain is illegal. The compounds can cause severe skin problems and ultimately, cancer. Hexavalent chromate is poisonous. These compounds are not excused from hazardous waste regulations where household wastes are.
These compounds are bad enough that government regulations mandate "elimination of hexavalent chromate by 2007 for corrosion protection."

Does your electrolyte turn yellow? That's a sign of chromates.

If you have been using stainless steel for the anodes (positive electrodes), wear rubber gloves when working with or near the liquids. If you need to dispose of it, allow it to evaporate into powders and dispose of the powders in sealed containers during your local "hazardous waste clean-up days".

Best bet - don't use stainless steel no matter how tempting it is.