I ran out of time last night to post.
Yesterday I completed the re-plating of the GS125's rear brake arm.
Brake arm de-greased then cleaned with Brass coated steel wire brush.
In the tank and plated for 15 minutes
With these settings
Not plated well, you can see the missed bits. I calculated (rough) 5 Square inches of surface area @100 mA per Square inch for 15 mins a strike.
Did 3 more strikes for 20 mins each at the previous settings to get a better coat, rinsed and buffed between coats.
you can see in the picture below where the zinc has not adhered to the metal in the hard to reach places, a media blast would get in there OK but I do not have access to blasting.
The part now had nearly an hour in the tank with 4 strikes. At this point the colour and texture of the surface were the same after the last 3 strikes, colour light-ish grey and smooth to the touch. I dried it with a heat gun and buffed with a soft brass wire brush. Time to raid the cupboard and add some "brightener" to the electrolyte. "Karo" Corn syrup gets a lot of thumbs up in the states but not available over here, so, from what I can gather it is pure Glucose - Dextrose type stuff and these are available via body building suppliers on Ebay. Only thing in the cupboard today is caster sugar, ah well it will have to do. The PH of my electrolyte is still on the low side (acid) at 4 via litmus paper so will have to make a new batch soon, having nothing to loose I added 100 grams of castor sugar, some recipes say same or more sugar as Epson Salt but I just want to try a little sugar for now just to see what happens.
Gave it 25 minutes, so longer than before but with less current, there was noticeably less bubbling with the lower current and a slightly shinny-er finish.
Rinsed, dried with hot air gun and buffed with soft brass brush and a light going over with Solvol. Shinny!!!!
Now for the small bits
Even with ACF50, GT85 and cold water rinsing the bike has a lot of corrosion on most of it's fasteners, I have found Stainless Steel Brake adjusters with spring on Ebay but Before I get the crow bar out to open my wallet I want to see if I can get some more winters out of what i have.
Here is the nut De-Rusted, It is full of pit marks.
5 mins later on the fine grinder and 600 wet and dry
That bar by the way is a M6 x 150 mm Stainless steel coach bolt.
Wiped with acetone and in the tank for 15 minutes 1 Volt 300 mA, must be 3 Sq-ins there? Came out a bit underdone.
So in for another few strikes 45 mins in total.
Not bad, after dying and a buff up.
Getting near Tea Time now. Realised as I was putting it all back together forgot to take the blooming spring off.
Quick de-grease and wire brush, acetone wipe and in for 15 minutes.
Dried and polished with my well used Autosol cloth
Gave it a total of 3 strikes, and all done
here is a before and after as a reward for reading all the way to the bottom of this.
Conclusions so far:
To vary the current in my setup I am adjusting the voltage (Ohm's Law)
Basic solution works well
6 litres of water (Filtered via coffee filter from the rain barrel)
200 ml Distilled White Vinegar.
150 Grams of Epson Salts
100 Grams Castor Sugar (used as "brightener" does make a small improvement in appearance to the freshly plated item.)
The washing up bowl is a good size for my heater but makes the distance between the Anodes and the work a bit to great, will try a higher current per square inch and - or longer strikes. Can see a depletion of the Zinc strips used for the anodes even after plating these small-ish parts.
de-grease (strong solution of all purpose cleaner @60 C)
wire brush de-rust
acetone or alcohol wipe
The above steps steps together with using different gloves for each step keep the work contaminant free and result in a good zinc adhesion.
Buff with soft brass wire brush after rinse and drying followed by light polishing gives a good shine comparable to bare polished steel.
Improvements and further steps.
Media blast parts.
Acid dip parts prior to 1st strike to remove any rust particles and etch the surface.
Glucose as a "brightener" and more of it.
Increase PH of solution to max PH 5 by using a lot less vinegar.
Aquarium air pump to constantly mix electrolyte.
Increase current per square inch to 140 mA
More accurate calculation on surface area of part and possible alteration of technique depending on the shape of part.
Now the rest of the bike end is letting it down.
Will monitor these parts this winter
More soon, may have to buy (Aghhhh!!!) some pasivate chemicals to get that bright Zinc look
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Last edited by linuxrob on Mon Dec 17, 2018 9:06 am, edited 1 time in total.