I few years back a large chunk of my brake lines were replaced due to a failure in my brake booster. Working on my vehicle now I can see the usual cost of driving on salty winter roads, the lines are starting to look rather corroded; to the point that in the name of preventative maintenance I'll be replacing them sooner rather than later. This time I would like them to last longer than a handful of years in the same climate as what caused the corrosion.

What steps in preparation (or install) of brake lines can be taken to decrease the effects of corrosion affecting them? Would painting help, perhaps some sort of undercoating material? Would anti-seize on the line's threads prevent them rusting to calipers and other components?

Given this is preventative maintenance and not a repair where loss of drivability is occurring, expect that I have as much time as needed to prepare the lines ahead of time for anything that may take several days to do before install.

4 Answers 4


You've got two choices as I see it here to prevent (or significantly reduce) exterior brake line rust:

  1. Use stainless steel brake lines. This is a great option, but SS lines (and I'm not talking about braided lines here) is a lot harder to use than regular steel. It is more prone to splitting. The ends have to be treated differently due to this. SS will significantly reduce the amount of corrosion which would be seen on the brake lines, though.
  2. When replacing the brake lines, cover them with something like POR15. This stuff bonds with, coats, and changes the metal making it impervious to rust. There are two caveats with this stuff, though. First, you cannot get it onto the fittings. if you do and then tighten it into the caliper or what have you, it will not come apart. It will weld the two pieces together, even worse than rust would do it. Secondly, it cannot be exposed to sunlight for a long period of time. If it is, it will degrade and allow for corrosion. This isn't a problem underneath the car, but thought I'd mention it.

Something else to consider with rusted brake lines. Ensure you are changing out the brake fluid every two years or sooner. Brake fluid collects water over time. This make it so the insides of the brake lines corrode as well. Not good to have the lines being eaten away from both sides at the same time.


Replace the lines with Copper-Nickel Brake line is the best solution imho, it will not corrode and is far cheaper and far easier to bend and flare than Stainless steel line. So sweet to work with. Problem solved.



  • it needs to be said, that cooper brake lines should not be used with aluminium cylinders, because of electro-chemical corrosion Aug 8, 2016 at 10:16

You have pretty much answered your own question. The spray can undercoating has done me well over the years. My personal experience on a 1984 Dodge that I sprayed was 18 years and one brake line. That was 18 New England winters. My 2002 Silverado (the only vehicle I didn't spray) it came from the dealer with some kind of waxy coating on the under carriage, all the lines were rusty after 6 years. The first line failed after 8 years. On a new vehicle you can't spray the side of the line where it sits on the frame though. I just spray a good heavy coat that fills the gap against the frame. I only apply anti-seize on the bleeders. It may be just a gut feeling but I can't imagine it would a good thing if it worked it way into an ABS module. The undercoating does a good job of protecting the fittings. Just be careful if you have to apply some heat to remove a component as the undercoating will burn and it generates an awful smell while burning.


Get a spray pump for olive oil or some such and spray everything down with diesel fuel every 3 couple of months. This will protect the steel and also start to freel up rusted bolts and the like.

  • My father uses hydraulic fluid. It's designed to stick and lubricate. He applies it with an old paint sprayer (for undercoating) hooked to an air compressor.
    – rpmerf
    Aug 1, 2016 at 12:33
  • Spray fuel all over the bottom of your vehicle... flammable fuel... right next to hot exhausts & brakes. Sounds like a terrible idea. Have a good reference that says it's not that bad? (Why would you want to "free up" all the bolts under the vehicle anyway, if you're not taking them off you WANT them to stay on!)
    – Xen2050
    May 31, 2017 at 2:19

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