Does Stainless Steel React to Concrete?

Minimal corrosion damage is anticipated over a 75-year service life. In new concrete with a pH of 12 to 13, between 7,000 and 8,000 ppm of chlorides are required to initiate corrosion of embedded steel. Corrosion of reinforcing steel and other embedded metals is the main cause of concrete deterioration. Embedded prestressing cords and other steel reinforcements, cables, lifting anchors, fixtures, rack angles and galvanized rebar corrode enough to crack your concrete and masonry coatings. If you need to maintain hydration on cold days, additions of up to 2% calcium chloride are believed to be fine, but they can be disastrous in steel-reinforced mortar and concrete that have a minimum internal relative humidity of 85%.

Galvanic corrosion presents a problem for hot-dip galvanized steel, whether dissimilar metals are subject to atmospheric exposure, or when embedded in concrete because the zinc coating is sacrificed for a metal other than the base steel, for which it was designed to protect. Although the natural tendency of steel is to undergo corrosion reactions, the alkaline environment of concrete (pH 12 to 1) provides steel with corrosion protection. As for stainless steel, once again, stainless steel is widely used for integrated rebar, and rebar suppliers should be able to advise on the relative advantages of type 316, compared to Edison's patented portland cement aluminum powder mixtures, since reactions later with the alkalis of portland cement release hydrogen gas. This creates foamed concrete useful for insulation purposes. So how does all this information relate to galvanic corrosion because different metals are in contact while they are embedded in concrete? If the black rebar (rebar) and the hot-dip galvanized rebar are in contact in the presence of an electrolyte, even when embedded in the concrete, the galvanized coating could be sacrificed by the black reinforcing bar connected instead of protecting the rebar below the galvanized coating. In conclusion, galvanic corrosion can still be a concern when hot-dip galvanized steel is embedded in concrete, but there are several methods to prevent it. The material provided herein has been developed to provide accurate and authoritative information about hot-dip galvanized steel after fabrication. Due to the inherent protection of concrete, reinforcing steel does not corrode in most concrete elements and structures.

I suggest you contact a supplier of galvanized and stainless rebar, who will have a wealth of experience and history in this issue. Carbonation-induced corrosion often occurs in areas of building facades that are exposed to rain, shaded by sunlight, and have a low concrete cover over reinforcing steel. It can attack and corrode steel, and regardless of pH it can cause corrosion in some grades of stainless steel, galvanized steel (by definition, galvanized coating is zinc) and aluminum.

Jack Brown
Jack Brown

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