How To Acid Stain Concrete With Rust Spots

How To Acid Stain Concrete With Rust Spots

Image Courtesy of DeLaughter’s Decorative Concrete (and doesn’t include rust spots).

You’ve bought your acid stain and prepared your concrete to apply it. Everything is ready for you to embark on your big project! That is, until you find rust spots on your concrete.

Why Concrete Rusts

Why does concrete rust? Well, it actually doesn’t - at least not by itself.

You’ll find that concrete doesn’t develop rust spots on its own. Instead, it receives the rust spots from objects placed on it or in it. As you know, metal chairs, planters or even a small piece of metal like a nail will rust when it rains. However, when these objects are touching the surface, the rust penetrates the pores of the concrete and fights to stay there. Even if these objects are later removed, the rust spot from them will remain.

Why You Shouldn’t Use Bleach

We are frequently asked if bleach can solve concrete rust woes. While this is an option, it’s not necessarily one we recommend. Bleaching will help make the rust disappear, but it will also discolor your concrete. That means when you stain your concrete, the bleach spot will stain differently from the rest of the surface. Basically, you’ll be trading one problem for another. The same goes for any other harsh cleaners.

Specific Stain Colors Will Help

Instead, we recommend using your acid stain to cover up the rust spots. When you stain over the rust, in some instances the acid in the stain will remove the spot. If not, then using the correct colors will camouflage the rust spot, allowing it to blend in and disappear to the eye. However, this will only work with specific color stains. The medium to darker browns, blacks and sometimes even Riverstone stains are the best bet for covering up the rust spot. Many times the red-based stains will even work. Keep in mind that you’ll have a more challenging time with the turquoise, greens and lighter colors.

Either way, we recommend performing acid stain tests of different colors before you commit to your entire concrete surface.

Be Creative by Highlighting Your Concrete

Another option is applying a highlighting coat. To do this, stain your concrete floors with a light or medium color. Once that stain dries, apply a highlighting coat, by holding your sprayer wand higher than normal and raising and lowering it as you work side to side and back and out, with the same or a darker color. This technique helps the rust spots become a part of the character instead of a blemish, while creating more color variances, highs, lows, and mottling.