What Causes Rust Stains On Concrete?

What Causes Rust Stains On Concrete?

Your driveway, sidewalk, or wall can stand up to heavy impacts without damage, but why is it that orange blotches develop so easily on these surfaces? Rust stains are almost as resilient as the concrete itself, and most homeowners would consider them irritating eyesores. But how exactly did they get there? Understanding how these unsightly marks developed may help you prevent more from sprouting in the future.

So how do these rust stains come to be?

For rust to develop, three key elements need to be present:

  • Metal
  • Water
  • Oxygen

Most of us learned this from an early age, but what does this have to do with concrete? It isn’t metal…right? We categorize concrete as a masonry material, and it is far from steel or aluminum. However, most cement mixtures contain small traces of metal. The most common metals found in them are:

  • Iron
  • Aluminum
  • Lead
  • Copper & copper alloys
  • Zinc
  • Cadmium

How does water cause rust stains on the concrete?

Now that we’ve identified that concrete does have metal in it, we need to discuss how the next ingredient comes into play: water. Rust forms through an oxidized reaction when the metal comes in contact with water and oxygen.

Concrete is a porous material. This means the pores along the surface and throughout it are larger and more open than a nonporous material such as plastic. Water can much more easily seep into the material and reach the small traces of metal embedded in the substance, and then form this reddish-brown oxide on the exterior part of the surface. Water also can reach the steel rods and other metal materials within a concrete structure, causing the oxidized reaction to occur and this orangish blotch to form.

Another common way these stains develop is from fertilizers. Chemicals found in these grass and plant foods also contain metals. They can include traces of:

  • Iron
  • Copper
  • Zinc

If fertilizer falls onto the masonry surface and comes into contact with water at some point, then all the elements needed to form rust are present. The reaction will take place, and stains will mark the surface as evidence of this reaction.

How can I remove these rust stains?

The best way to remove these blotches and streaks is with a pressure or power washer and a commercial-grade cleaning solution. TidalWashers’s, Red Fighter, is the best solution for effectively cleaning away rust from wood, masonry, and other exposed hard surfaces.

Looking to buy?

Shop our products at Tidalwashers here, or reach out to one of our expert team members to find the best product for your cleaning needs.

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