Rust removers and rust converters are different products. Choose a treatment made for the metal and its intended use; do not improvise a mixture of commercial chemicals.

Removal or conversion?

A remover dissolves or loosens corrosion so it can be removed. A converter reacts with suitable rust and may leave a coating that needs an approved protective finish. Neither repairs weakened metal. Color changes alone do not prove that a treatment is complete.

A safer approach

1. Identify the metal, coating, and purpose of the object. For structural parts, blades, or valuable tools, seek appropriate professional advice.
2. Read the product label and safety data sheet. Use only on listed materials, with the specified gloves, eye protection, and ventilation.
3. Clean and prepare the surface as directed. Apply the product without adding tannic acid, water, or another cleaner unless the manufacturer explicitly directs it.
4. Follow that product’s contact time, removal or rinsing instructions, drying time, and compatible protective finish. Keep chemicals away from food and food-preparation tools.

Food-contact tools and cast iron

Do not assume that a product is suitable for knives or cookware because one ingredient is called food-grade. For cooking surfaces, use the cookware manufacturer’s rust-removal and reseasoning method. Do not apply automotive undercoatings or general-purpose chemical treatments to food-contact surfaces.