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I always hate when I can't find a yellow zinc bolt for my car and have to settle for a shiny silver bolt from the hardware store. I recently discovered the ultimate solution! Caswell plating is best known for its Copy Cad system of zinc plating and cad-look zinc plating. It's a fairly involved process with tanks, heaters, agitators, power supplies, etc. However, one of the things they sell is Yellow Chromate -- the stuff used to turn silver zinc into yellow zinc like all the bolts on our cars. The beauty of this stuff is that it's cheap ($35 for a bottle that will last a very long time) and super easy to use. Just mix an once of the chromate in a gallon of distilled water and you're pretty much ready to go. Take a new silver bolt, degrease it, and dip it in the yellow chromate for about 30 seconds. Then dip it in distilled water and let it dry for at least a day before touching it. It ends up a yellow zinc bolt like all the others on the car. You can adjust the darkness by using more chromate and/or leaving it in longer, and there is no heater or power supply or other stuff needed. It can help to dip the bolt in a light muriatic acid solution (about a cup of pool acid in a gallon of distilled water), but it's not entirely necessary. Here's a cheap flange head bolt before and after... Whole process took less than a minute, and just needs a day for the yellow to harden up...
Nice, I missed that. I've mostly ignored the mass migration to FB. Come to think of it, I think I was the last guy to finally leave the old mailing list too. I just thought it was cool that you don't need to set up a whole plating situation to turn silver bolts into yellow zinc. Seems like a lot of guys who don't want to do to the trouble of plating themselves might be interested in a $35 hack to convert shiny silver bolts.
That said, I've been working on plating too... Here are some parts off an old Mercedes I've been restoring....
That looks fantastic Tom!
I've been intrigued by those plating solutions from Caswell ever since I discovered them, but never pulled the trigger. Now I will, thanks.
That looks fantastic Tom!
I've been intrigued by those plating solutions from Caswell ever since I discovered them, but never pulled the trigger. Now I will, thanks.
If you do, find a nice 10 amp current-limiting power supply at the same time. The kit doesn't come with one, and you'll need it to plate anything. I have a 3 amp power supply and it's big enough for small parts, but anything bigger than the parts I posted would benefit from more current. You can save money by reading up and making your own solutions. Caswell makes it easy by including all the solutions and buckets in a kit, but at a fairly hefty margin I think. I always wondered if the Copy Cad looked ok, etc. and thought it was some lesser version of plating. The original Copy Cad is nothing more than traditional zinc plating without any brighteners, followed by chromating for color. When you add the brightener and use the yellow chromate after plating, it's not a "copy" of anything -- it's the same as any old yellow zinc part. If I were plating an entire engine bay I'd still send it out, but for one-off parts you remove when repairing something, being able to plate a part or two in the garage is awesome...
If you need a massive load done let me know. A fellow RL'r gave me name of a good source in Calgary where I got my stuff done....can't remember if you saw my post a while back. I understand it's hard to find places to do it in the US with EPA reg's
I thoroughly enjoyed the zinc plating run I did, I would recommend it to anyone looking for a neat project. I don't have any parts left to do, except for some larger parts I'm outsourcing. My final iteration of the plating rig had a fish tank pump and a copper bar used to hang parts on.
If I had to do it again I would probably go with the Caswell kit. I just didn't want to invest that much into it at first since it was just an experiment. But even with the DIY setup I was getting great results. I use the Caswell chromate as well.
That is cool! This might be a silly question, but are typical silver coloured hardware store bolts always zinc plated already? Also, does this actually make any difference to corrosion resistance? I remember when I was getting a set of spring plates zinc plated, they did them in silver zinc first by mistake. When I discovered this I initially told them it was fine, I didn't care too much about the colour. But the guy said it makes a huge difference to how well they resist corrosion, and insisted that I let them re-do it in yellow.
Silver is zinc plated, as you said. This is natural finish before any post-process is done. In general mass-produced parts have some sort of post-process done as described below:
What you generally see at the hardware store and etc is a "clear zinc" chromate post-process, it doesn't change the color. Chromate is just a quick dip in a chemical bath, as posted by Tom in the first post. It does in fact add another (measurable) level of protection, but not a huge one... for example the difference between zinc plating and no plating at all. The chromate will degrade before the zinc is touched, and then the zinc degrades sacrificially before the steel part will.
Chromates are available in different colors, depending on the acid base used when concocting it. You can even get green and black, although yellow is most prevalent after clear. That's why it's called yellow zinc: it's zinc plated, and chromated with a solution that imparts a yellow color.
If you do, find a nice 10 amp current-limiting power supply at the same time. The kit doesn't come with one, and you'll need it to plate anything. I have a 3 amp power supply and it's big enough for small parts, but anything bigger than the parts I posted would benefit from more current. You can save money by reading up and making your own solutions. Caswell makes it easy by including all the solutions and buckets in a kit, but at a fairly hefty margin I think. I always wondered if the Copy Cad looked ok, etc. and thought it was some lesser version of plating. The original Copy Cad is nothing more than traditional zinc plating without any brighteners, followed by chromating for color. When you add the brightener and use the yellow chromate after plating, it's not a "copy" of anything -- it's the same as any old yellow zinc part. If I were plating an entire engine bay I'd still send it out, but for one-off parts you remove when repairing something, being able to plate a part or two in the garage is awesome...
04-21-2018, 08:56 PM
Yellow Zinc Bolt Nirvana
