Tetra Gun Blue & Rust remover Gun blue and rust remover is the safe, reliable solution that removes rust and old blue easily and quickly without damaging base metal. removes old metal finishes from modern firearms, muzzleloaders and antiques. Excellent for removing rust from tools, gages, and precision equipment. Available in a 3 oz. wide mouth container. Liquid gun blue is the best product for steel touch up or complete re-blue. Fast acting liquid gives a non streaky uniform blue/black finish. Additive package further enriches color and reduces desired color achievement time.