Walmart offers the Evapo-Rust The Original Super Safe Rust Remover 1-Gallon Bottle, model no. ER012, for $14.88. (Amazon has it for the same price with free shipping for Prime members.) Opt for in-store pickup to avoid the $4.97 shipping fee. That's tied with our mention from last week as the lowest price we've seen. (It's the best deal now by $12.) This biodegradable rust remover is non-toxic and non-corrosive.