Rust erasers promise to rub away the unsightly corrosion that can build up carbon-steel knives. We tested five models to see if any would be worth buying.
Published Mar. 1, 2015.
Rust erasers, made from a rubber compound surrounded by a medium- or fine-grit abrasive, are designed to rub away the unsightly corrosion that can build up on and damage carbon-steel knives by removing small amounts of the rusted metal from the surface. (Rust should not be confused with patina, a beneficial form of oxidation that affects only the outer surface of the metal, turning it charcoal-gray and protecting it against rust.) You simply lubricate the eraser’s surface with water and rub it gently along the knife’s blade with the grain (these products can leave scratches, so it’s best to move back and forth in the same direction while following the metal’s grain). We tested two models (priced at $5.73 and $7.29), both medium-grit (the style sold by most companies; experts told us that the scratch pattern it leaves behind most closely resembles the existing grain of most carbon-steel knives). We let new carbon-steel knives air dry and develop rust, scrubbed them, and repeated the process three times. We also let three additional new carbon-steel knives rust and compared the erasers with more common household products: medium-grit sandpaper, metal polish, and a mild kitchen cleansing powder.
All five products removed rust effectively after just 3 to 4 minutes of gentle scrubbing per side. However, they revealed black marks where the rust had been that indicated “pitting corrosion”—that is, tiny holes where the corroded metal was removed. Fortunately, a knife expert reassured us that the tiny pits won’t weaken the strength of the blade as long as it doesn’t rust further and require more erasing that would remove more metal.
Ultimately, we preferred the dedicated erasers for their ease of use. The polish and the powder required us to dirty kitchen towels to scrub them into the metal surface, while the sandpaper was slightly less nimble and difficult to maneuver on the knife’s sharp corners. Of the two erasers, one model proved exceptionally durable, remaining coarse and sturdy after repeated scrubbing on sharp edges and tight corners, while another crumbled and its abrasive grit wore down. Though we’re always careful to thoroughly dry our carbon-steel knives so that they won’t rust, we’ll keep the erasers on hand for emergencies.
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