Liquid 4-Liter Refill - Non-Hazmat, Non-Flammable & Non-ToxicCorrosion Block is a clean fluid that actively protects metal using advanced polar bonding chemistry. Synthetic additives in Corrosion Block completely penetrate corrosion cells…replacing the salt water which is then allowed to evaporate. Corrosion Block’s hydrophobic film remains to further protect the metal acting like an “OFF SWITCH” for corrosion. Unlike waxy products Corrosion Block then leaves a clean clear moisture