Over the last few years, corrosion of ties, anchors, and joint reinforcement has become a main concern within the masonry industry. How much galvanizing is required to protect against corrosion? When should stainless steel be used? ZINC GALVANIZING Galvanizing is the traditional way to protect metals from corroding inside masonry. Zinc galvanizing protects steel in two ways. It prevents moisture and oxygen from reaching the steel. Without moisture and oxygen the steel can't corrode. And by migrating to exposed steel areas, the zinc sacrifices itself, corroding before allowing the steel to corrode. This latter process is called galvanic protection. STAINLESS STEEL Stainless steel isn't required but some designers prefer to use it because the life of galvanizing is unpredictable. Stainless steel costs 5 to 10 times more than zinc galvanizing but it can last much longer. The correct type of stainless steel to use is the high nickel-chrome stainless steel conforming to ASTM A 167, Type 304. Classified as austenitic, this type of stainless steel has the best corrosion resistance and doesn't develop red rust. AVOID DISSIMILAR METALS When dissimilar metals are used together, an electrical potential (voltage) is often created between them. The result is corrosion. The more positively charged metal (the anode) corrodes, sacrificing itself to the more negatively charged metal (the cathode). The difference in electrical potential between metals is not the only factor that influences corrosion. Important also is the density of the corrosion current. If the surface area of the anode is much smaller than the surface area of the cathode, the current density will be high and the anode will corrode rapidly.