I'm working on a Trex to aluminum staircase for my porch that I built last fall, and I used black zinc screws because they looked great with the black slats. However, I've noticed that the screws have turned rust-colored. It's frustrating because while I can scrub them back to black, I don't want to keep doing that. The place I bought the screws from said they should be treated like stainless steel, meaning they shouldn't rust or discolor. I really prefer the black finish over stainless, which I find too industrial-looking. If I need to replace them, what type of screws should I consider that wouldn't discolor? They need to be machine thread to go through the Trex and aluminum into a nut on the back side, and I'd like to keep the nuts and washers black zinc as well.
2 Answers
It sounds like your screws might be reacting with the aluminum, which can lead to galvanic corrosion. Avoiding that would mean you should ensure there's no direct contact between dissimilar metals. Maybe look for some high-quality coated screws that specify rust resistance? If you really want to stick with the aesthetic, there are black stainless screws out there that might work better.
I get your concern with the style! If the stainless looks too stark, think about trying black oxide coated screws. They can provide a similar look to black zinc but with better corrosion resistance. Just make sure they’re rated for outdoor use!
Black oxide is a great suggestion! I used those for my project and they held up really well.
Good point! I've also heard that having a barrier, like a thick paint or sealant, can help reduce corrosion. It might be worth exploring some options.