So, the zinc plating on the parts associated with the steering head was completed. The parts started out looking like this:
After plating, they look like this:
I wasn't going for a perfect finish, so I didn't spend a lot of time polishing the parts before plating. That said, they all have a decent layer of zinc, and look far better than before, though you can see a little anode shadowing on the larger parts.
The process was pretty simple. First I did a rough wire brush/wheel, and then dipped the steel parts into phosphoric acid (Etch and Prep from Home Depot, or Naval Jelly).
You could also use Muriatic acid, but it's nasty stuff and has a bad habit of rusting everything within 6 feet of an open bottle. I guess you could also use other rust killers like Evaporust, though phosphoric acid leaves a layer or iron phosphate behind which is a good thing... helps to prevent corrosion and zinc sticks to it well. Even though it's fairly dilute, you do
not want to leave soft iron (bolts, cast iron) in the solution for too long as it will slowly but surely convert the entire piece into iron phosphate... I left a 10mm bolt in there for a week by accident, and it was uniformly shrunk down to about 3mm.
Once the rust was removed, the parts were washed in baking soda/water, then washed in distilled water and left in it until plating. when ready for plating, the parts were washed in acetone, dried, hung from copper wire, and then placed into the electrolyte solution.
I'm using the Epsom Salts and vinegar electrolyte, along with glucose and Sweet and Lo for a brightener. I'll probably experiment with zinc chlorate and zinc sulphate in the future, but again, I wasn't going for the super bright look, just something roughly like the original bright zinc. I had the anode and cathode connected to my lab power supply... it has variable and fixed voltage supplies, and can supply up to 1A.
I had to experiment a bit to get the amperage down to a low enough level: on small parts this was down to about 0.5V and around 100mA. Over the years I've found that you're better going for a lower amperage, even if it takes more time. You end up with a more uniform layer of zinc, and it tends to be brighter. After a period of time, the parts will look dull and grey:
At this point it's usually a good idea to take them out and "card" them... give them a rough polish with a stainless brush, scotchbrite, and then maybe steel wool... the more careful you are, the better the parts will come out in terms of smoothness and brightness. I did a rough carding... no steel wool, because I was just looking for a good layer of zinc, not perfection. After carding, the parts go back in, and you rinse and repeat until you have enough zinc on the parts. After a final carding, here is how some of the bits came out:
Once the bits were done, I started looking at putting the tapered roller bearings in. I started cleaning out the mating surfaces for the bearings, and I found this:
There was a small lip in there where it seems someone did a poor job of replacing the bearings in the past. There was other scouring in there too... I cleaned it up, put the race into the freezer, and then pressed them into the head using a home-made puller/press.
Again, these are tapered roller bearings for the earlier Ducati's and they seem to fit fine, though the fit was a bit looser than I'd like... I'm pretty sure that's caused by the bodged job that someone did before. I'm tempted to drift them back out and put a drop of loctite on there just to be safe (thoughts?).
I hope to get the steering stem etc. dry assembled tomorrow to verify the fit, but right now it looks good. I hope to turn out some new bits for the swingarm next week so I can get that back together.