Home Zinc plating experiments

Finally got round to doing a few more bits with the home brew plating bath. I did try some experimentation to get a brighter finish out of the bath instead of a gray. I used my standard recipe:

100g of Epsom Salts from Pound Stretcher £1.00 per 500g (Magnesium Sulphate MgSO4) per litre of white distilled Vinegar via ASDA 39p for 548ml. Containers from the local Greggs, other sandwich shops are available. Used a 3 litre one for the electrolyte and the 1.5 ltr ones as rinse tanks. Splashed out on some new anodes too, got 5 X 140mm x 140mm x 0.2mm thick 99.9% zinc sheets for £6.52.

Made up the electrolyte and dropped the remains of the old zinc anodes in and left it overnight to dissolve a bit of zinc in the solution. Next day used 4 of the 5 new anodes to line the inside of the 3ltr tub and some Titanium wire in a ring around the tub to secure them. Will use crocodile clips in the future for a better connection. Further modifications to complement the aquarium heater were the addition of an eBay sourced 12V small pump and a cathode bar made from 2 lengths of 6mm twin and earth copper wire soldered together and insulated where it goes over the edges of the tub see pic below without the heater i filter the mix via a coffee filter after every session into a clean 5Ltr container.

By this time I had read a lot about the process and ways other than proprietary chemicals to get a bright finish out of the tank without the need to buff. I made a few solutions to my recipe and added the following:

Dextrin or pure glucose @ 3g per litre and got a slightly lighter gray but still matt, slowed the plating down a bit too. - Abandoned.

PVA glue, the clear type @ 4ml per litre as a wetting and levelling agent with and without the glucose @ 3g per litre got very light gray but slow plating and reduced the conductivity of the bath too much. - Abandoned

Vanillin @ 1-3g per litre, this is used in food prep and is a synthetic alternative to Vanilla. Ethyl Vanillin is the compound that gives the best results in tests but is expensive and difficult to get so I had a go with Vanillin, again from ebay. It did give a shinier lustre out of the bath and made the mix smell a lot better (vanilla) the more I added the better the look was. On close examination the coating was satin and had a glittery roughish look even when slightly buffed. Slowed the plating down a lot. Well worth trying if this is the finish you want but I am after a Cadmium silvery type look. So put this mix in a container for later use maybe.

Some examples of Vanillin at 1 g per litre

and 3 g per litre

So after all this I thought I would try some passivating chemicals and stick to a std plane mix to get a good even gray coat then buff and clear passivate for protection and keep the silvery look. Ordered the Clear / yellow and Olive drab from Gateros plating. This turned out to be a good idea and am now getting with the clear passivate a very good cadmium look. I use the mix @ 30c with circulation pump on and 3 12 minute strikes with buffing in between and a final buff and gegrease before in the passivate for 30 seconds.

my 4 rear disc bolts for the Z500 project

Got some time after Christmas to give the GS125 som TLC to the chain and will plate the rear spindle, spacers and chain adjusters. Will also redo the rear brake arm as now after over a month in the salt has dulled down a bit even after cold water washes and gt85. Then busy with the Z500

All the best to everyone.

Rob B

Evening all hope you had a great break. Took advantage of time off and good weather and got the rear wheel out and chain off the GS125. First an update, the rear brake arm has now had 6 weeks of salt and has not fared well. It did have a good layer of zinc but the coating was not passivated to give it more protection.

I now have some clear passivate chemicals to play with and see how much more protection it gives. The chain and sprockets are to be replaced in the spring but it is due a good clean and oil, being a non -O ring chain I cannot overlook it. As you can see in my before and after shot below when I first replated the brake arm the rear spindle and chain adjusters were in a terrible state.

Put the chain into soak in old engine old for a bit while I cleaned up the spindle etc. I took the sprocket off to and cleaned up the carrier bolts and tabs. Whilst there I noticed a bit of roughness in one of the wheel bearings so will fit a new set in the spring before MOT time. A 6302 on one side and 6202 on the other. The sprocket carrier bearing is OK but will order a 6204 for it anyway.

Those tabs have not a lot of life left in them, good job I ordered a new set with the chain and sprockets.

On with the plating:

Filtered my electrolyte mixture via a coffee filter into the plating tank and let the heater get the mix up to 30 C with the circulating pump on.

First up were the sprocket bolts, these are 8mm x 1.25 pitch and work out at 2 square inches surface area each. I can do 2 at a time with a total current of between 400 and 550mA. I chose 500mA so adjusted my voltage to give me this, the first strike as usual is for 15 minutes.

Did 3 strikes on these followed by the other 2 carrier bolts. 3 strikes on the pair of tabs and then did all 4 nuts together. Improved my spreadsheet to calculate the nuts surface areas as well as bolts now. Each 8mm std nut works out at 1 square inch total surface area would you believe copy of spreadsheet available on request.

By now my passivate mix had heated up to 25 C in a water bath so the bits got a clean with acetone , dried and in for 30 seconds. They came out with the Cadmium look I was looking for. Interestingly the passivation process with my setup of Vinegar and Epson salts dulls the mirror like shine when buffed to a bright silver when done.

I need to clean the nut threads better, will look out for a small wire bottle type brush. The dark rings round the bolt shoulder show that I have not got all the rust / grease of that part either. Must do better.

Spindle nut, spacers and adjusters proved no problem but the spindle itself was too long for the tank. I could have just stood it up on each end but that would mean that the very bottom and top not getting any coating. After some Heath Robinson type ideas i just made a small wood support over the tank with the spindle pushed through a hole in the cross piece and held at the right height by a cloths peg first one end then the other. I was too embarrassed to photograph this "contraption" but I am sure a) you could imagine it, and b) have a much better idea.

Whilst all this plating was going on I not only cleaned and oiled the chain but cleaned and repainted the rear of the swing arm as it was now letting the side down.

And some pics of the finished job, and before anyone comments I forgot to give the bike a wash before i did all this so the chain guard is looking a mess, sorry.

Regards and have a good 2019

Rob B

Will update this thread shortly, am now using proper chemicals