Author Topic: Zinc Plating  (Read 1604 times)

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Offline Gamma

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Zinc Plating
« on: February 23, 2017, 06:56:29 am »
This is what I do for my Zinc plating after I researched it on the net.
It’s a simple procedure, but it is quite time consuming, so it’s only good if you’ve got plenty of spare time. I shall also add photos.
I use a plastic food box and dissolve 300 grams of Epsom salts (Magnesium sulphate powder) and 100 grams of Zinc Sulphate powder and also 10 of those Sweet and low sachets (make sure they are the ones that contain Saccharine) in (4 litres approx) of White vinegar (can be topped up with distilled water if needed)
The sweet and low is a brightener

For cleaning, I use Hyrochloric acid at 30% (Muriatic acid) also called pool acid as its used in swimming pools, which is where I got mine from.  This is used to remove rust and old plating. I think that this is really important in the process, as it really does a good job, leaving the parts super clean and ready for plating.
I use distilled water to rinse the parts
I use a cheap fish tank air pump to circulate the solution. I do this by using the plastic grill that is supplied with some of these plastic food boxes to tie the air tube in loops on the bottom with cotton, then I punch lots of holes in the tube with a needle, so you get bubbles right across the bath.

I drop a bigger long flat lump of zinc into the solution to hold this plastic grill down as it will float otherwise. (don’t leave any Zinc plate in the solution whilst not in use, as it slowly gets eaten away and increases the zinc in the solution, the increase is good, but you end up with no zinc plate)
I don’t heat the bath, just do it in a warm room.
I use a cheap transformer to drop the mains voltage to about 6 volts

I then feed the 6 volts into a cheap digital regulator
I adjust the output voltage to 3 volts and typically adjust the output amps to from between 0.14 to 0.5amps

I use a piece of copper pipe on the top of the box (I melted 2 grooves in the plastic with a soldering iron so it doesn’t roll about
I use 4 pieces of high purity Zinc sheet 2 each side of the box

I wire it all up so that the copper pipe is connected to the cathode (negative side) and the Zinc plates are wired together to the anode side (positive)
I hang the parts in the bath using copper wire and also use this wire while dipping the parts in the acid as it is not effected by the acid
The wire is stripped from cable which is usually called (twin and earth)

When you have prepared your solution and all is ready to go, fish pump working and check that you are getting volts between your copper pipe and zinc plate (use a cheap multimeter to check) set the volts to 3 and the output amps to 0.14
Clean and degrease the part or parts you wish to plate using a soup solution, I just use washing up liquid and brushes, but it depends on how dirty the component is, you may need white spirit or similar first. Prior to plating, the parts must be grease free. I then hang the part in the Hydrochloric acid, you must use a mask and rubber gloves, the fumes are very noxious and you must do this outside.  I don’t do it for a particular length of time I just keep checking until all the rust and previous plating has gone, it normally only takes a couple of minutes, then, dip the part in distilled water to rinse it.
From now on only touch the part with rubber surgical gloves, so as not to contaminate it with hand sweat etc:  If I think there may still be oil or grease present I wash the part again with washing up liquid, rinse it under the tap and then pop back in the acid for a final clean, then into the distilled water.
At this point when you remove from the acid you must immediately hang the part in the plating bath and turn on the power supply. (if you don’t the part will flash rust within a few minutes)  I typically can hang 4 or 5 bits at a time. Several small bolts can be wound onto a single piece of copper wire.
The parts should start to turn grey. I typically time this operation for 30 minutes.  Then wearing your surgical gloves remove the one of the parts and using a brass wire brush clean the part all over. I use a brass wire brush which is long, the short ones are not as easy to use because the stroke is too short. I also use scotchbrite for this. You should see areas of zinc plate shining through, but typically it may not be obvious on the first operation(strike). Then dip and rinse the part in the tub of distilled water, that you remembered to bring in from outside.  Then I pop the part back in the plating bath for another 30 minutes, meanwhile I take another part out and do the same. I do this operation about 4 to 6 times on each part depending on how thick you want the zinc plate and how the coverage is coming along.  Eventually you should end up with a shiny component.
When you get a full coverage of grey like the spring in the photo, you know you are on the way to a good finish.
For bigger parts use more milliamps, you really have to experiment with this, but if your plating finish is turning out rough, it is normally because your milliamps are too high, its better to use lower milliamps and do more operations. If you are not happy and the finish is rough or contanimated, it’s just a matter of dipping the part back in the acid and starting over.
When I am happy I dry the part and then polish with Solvol Autosol.
I have read that after Zinc plating, a more corrosion resistant finish can be achieved by Chromic conversion (passivation), (dipping in another solution) but I don’t have access to this out here.
When I tried it the first time, I thought that the grey finish was it, and was disappointed until I started brushing with a Brass wire brush.  I thought the brush would remove the plating, but it doesn’t
When I was first using the Hydrochloric acid to clean the parts on my work bench in my accommodation out here in Saudi, I noticed several things on the bench were rusting quickly, and the new Kawaski 1000 behind me in the room (my mate’s bike who I share a villa with) was getting surface rust on its discs and chain, I realise there was a problem.
The fumes given off by the acid (Hydrogen Chloride) mix with the moisture in the air becomes acid again and corrodes anything in the area. (use it outside)
The long bar that operates the carb bank can be done. It looks like it is chrome plated which is on copper plate. The chrome comes off leaving the copper which I plated with zinc, measure the diametre between strikes, to make sure the diameter doesn’t get too big.
I dropped one of the chrome plated slide operating forks into the acid hoping to just remove the chrome as its also copper plated. This was not a good move as the screw threads are a way for the acid to get to the aluminium or whatever light alloy is. I did
not monitor this as I was distracted, and went back out to a volcano eruption, lots of gas, and very little left of the part
For the wheel spacers, I used tape to hold a thin zinc strip inside to do the internal area. Maybe that’s a bit overkill
Zinc plating can cause hydrogen embrittlement in high tensile steel parts, caused by the hydrogen ions getting trapped under the plating and joining together and becoming molecules, when this happens the hydrogen molecules expand causing fractures. The normal remedy is baking, I have only plated one part that I considered vunerable to this which was a rear spocket. I cooked it in the oven at about 200c for 3 hours

Good Luck

Offline Gamma

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Offline Korven

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Re: Zinc Plating
« Reply #2 on: February 06, 2019, 12:01:45 am »
Not getting any coverage in deeper holes, any tip? Im not using a pump so maybe thats one flaw. Great guide!

Offline BobbyR

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Re: Zinc Plating
« Reply #3 on: February 06, 2019, 09:13:26 am »
That is a terrific write up, you should put it in Tips and Tricks so others could benefit.
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

But we were boys, and boys will be boys, and so they will. To us, everything was dangerous, but what of that? Had we not been made to live forever?

Offline RockCityCyclist

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Re: Zinc Plating
« Reply #4 on: March 05, 2019, 07:37:22 pm »
I've done the same thing and have had great results. Most of my hardware is looking good as new! Definitely recommend anyone that is considering new hardware for cosmetic reasons to try this out first.

Instead of saccharin I used Miralax. Miralax is polyethylene glycol 3350, which I used as my "brightener". (My wife bought a bottle for a backed up infant a couple years ago.) I will have to give the saccharin a try and see the difference between the two.