New Tool to Spot Microbial Metal Rust on Steel

You know how simple metal rust can cause big trouble, like leaks that hurt the environment? But did you know microscopic critters can also cause metal to rust? Yep, tiny organisms can create what’s called microbiologically influenced corrosion (MIC). This is different from regular rust (abiotic corrosion), and scientists have created a new test kit to tell the two apart. Imagine a little 10 mL bottle that acts like a mini laboratory. Inside, there are two tiny metal detectors (electrodes) that measure how much metal is rusting. Scientists used this kit to compare how different bacteria affect metal rusting. For regular rust, they used CO2 and acetic acid. For the microscopic rust, they used three different types of bacteria: sulfate-reducing bugs, nitrate-reducing bugs, and a mix from oil fields. When they looked at how the metal was rusting, they found that the normal rust didn’t change much. But with the microscopic rust, things were different. The Tafel curve, which shows how fast the metal is rusting, looked weird (distorted) and shifted around. Plus, the polarization resistance (how hard it is for rust to happen) changed faster with the microscopic rust. The kit could also tell if special chemicals (mediators) or germ-killers (biocides) were affecting the rust. Regular rust didn’t care, but the microscopic rust reacted to these chemicals differently. This new kit is like a superhero tool for scientists. It helps them figure out if tiny critters are causing metal to rust and how well germ-killers work against these tiny rust-makers.