Is this caliper zinc coated?

[Owen Lucas]

The reason I ask is that I will be putting the external sliding part of the caliper in an ultrasonic cleaner before I reassemble the brakes. I'm new to ultrasonic cleaning and the solutions that are used. I want to make sure I use the correct solvent since I've read zinc coated items can blemish with the wrong cleaning agents.

 

[vavavroom]

I think you can use a drop of copper sulfate solution to test for zinc. Apply a drop to the caliper. If the wet spot turns black there is a zinc coating. Copper sulfate is sold as root killer.

 

[Warstud]

If there Zinc coated they probably wouldn't look that bad

 

[Warstud]

I wire wheeled my calipers when I replaced my brakes . Then cleaned/primed then painted them with Krylon a couple years ago and they still look good.

 

[KrisZ]

What is there to blemish? The rust tells me that even if they were coated, that is long gone.

 

[FowVay]

I once replaced a front brake caliper for a neighbor. They purchased a rebuilt item from O'Reilly's Auto Parts. Out of the box the caliper looked like a brand new unit - clean, shiny, perfect. Within a year the caliper was hideous and completely covered in rust. That rebuilt unit had absolutely zero form of corrosion inhibitor applied to it.

I live in the south where a brake caliper will look pristine for many years (except for the associated brake dust). If I ever replace a cheap rebuilt unit from the auto parts store I will insist on it being cleaned and painted before installing.

I don't know where the OP is located but the fact that the caliper isn't completely rusted out tells me that there was a coating on the caliper at one time. Obviously it's been worn off or was cheaply applied to begin with.

Flush the brake fluid regularly to prevent this from happening to the inside!!

 

[930.engineering]

Is this caliper zinc coated?

Most probably yes. Very most calipers are zinc coated.
That's why the sliding part should be cleaned by using
a nylon brush only. Preferably at least.
.

 

[Owen Lucas]

What is there to blemish? The rust tells me that even if they were coated, that is long gone.

That's what I am trying to figure out, I've read that if there is any zinc coating, it can turn black in an ultrasonic cleaner with the wrong cleaning agent.

I don't know where the OP is located but the fact that the caliper isn't completely rusted out tells me that there was a coating on the caliper at one time. Obviously it's been worn off or was cheaply applied to begin with.

These are the OE calipers, 17 years old, 180k + miles and yearly salty winters. Not bad for the experience I'd say, they looked great for the majority of the last decade. The rear calipers aren't worth saving, but since the fronts work great, I will restore them as best I can. I'll give them a paint job as you recommend once they are cleaned up. I flushed the brake fluid recently....because the master cylinder failed.

Most probably yes. Very most calipers are zinc coated.
That's why the sliding part should be cleaned by using
a nylon brush only. Preferably at least.
.

Thank you for the nylon brush advice, I'll be disassembling the outside caliper but not the piston side, not sure if I want to experiment with that level of overhauling.

Since I'm probably dealing with zinc, I'll find a zinc friendly ultrasonic cleaning agent.

 

[KrisZ]

Ok since you provided more info here is my opinion.

If you’re planning to paint the calipers anyways, then it’s irrelevant of the zinc coating turns black or discolors some other way, it will still be there as normal cleaning solutions will not remove it.

If you will be submerging the whole caliper in the ultrasonic cleaner, I would recommend you disassemble the whole thing and remove all plastic/rubber components. Otherwise they may get damaged or react with the solution.

Besides, if you’re already this deep into reconditioning them, it makes no sense not to change the piston seals. The piston itself may have rust pitting at this age/miles, so it should be inspected at the very least.

 

[Owen Lucas]

Besides, if you’re already this deep into reconditioning them, it makes no sense not to change the piston seals. The piston itself may have rust pitting at this age/miles, so it should be inspected at the very least.

Those are good points. The OE overhaul kit is $45. Might as well completely disassemble and clean the caliper from the inside out if I'll be overhauling it. Some high temp spray paint and it's done.

 

[Carmudgeon]

I wire wheeled my calipers when I replaced my brakes . Then cleaned/primed then painted them with Krylon a couple years ago and they still look good.

That's what I did, a rebuild and painted silver. Used Rustoleum because it had the highest temp rating of the available "caliper" paints.

Outside of a chemical bath, or blasting cabinet, neither of which I had, a wire wheel worked better, and much cheaper than brake cleaner+hand labor.