Why is my Concrete Bleeding Rust (Video)

“Hi, my name is Greg Batista here to answer another question from the internet.

busyguy345 asks: Why does my condo wall look like it’s literally bleeding rust stains?

Those orange streaks are rust from corroding reinforcing steel — what engineers call rebar — inside the concrete. In South Florida, salt air and humidity are constant, and once they penetrate concrete, they reach the steel. When steel corrodes, the rust can expand to four to ten times the volume of the original steel, creating enormous internal pressure. That expansion cracks the concrete, and the rust pushes outward, leaving behind the stains you see on walls and ceilings.

This isn’t just cosmetic. The NACE/AMPP corrosion study estimated corrosion costs the U.S. over $276 billion annually — about 3% of GDP. In buildings, unchecked corrosion leads to spalling, falling concrete, and serious safety issues. Painting over stains won’t solve the problem. The right fix means removing deteriorated concrete, cleaning or replacing the rebar, and properly patching with engineered repair mortar.

For more content, follow me. Please comment since I personally read all of them. Ask me a question — I may feature the answer in an upcoming video.

Authoritative references: American Concrete Institute (ACI 222R – Corrosion of Metals in Concrete); International Concrete Repair Institute (ICRI guidelines); NACE/AMPP Corrosion Costs study.

The author, Greg Batista, PE, CGC, SI is owner of G. Batista Engineering & Construction and is a nationally-recognized engineer and contractor with more than 35 years of experience and offices in Fort Lauderdale, Florida.