Electrochemical Behavior of Steel in Calcium Magnesium Acetate

Abstract

Calcium magnesium acetate (CMA) is a term used to describe the reaction product of acetic acid and dolomitic limestone. This product is a mixture of calcium acetate and magnesium acetate and hes been identified as a possible deicing chemical to replace chloride-containing chemicals such as sodium chloride and calcium chloride. The Federal Highway Administration has sponsored work to determine the corrosive behavior of CMA on bridge structural materials and steel in concrete.Electrochemical tests ware conducted in commercial and reagent-grade CMA solutions of 0.5 to 20 wt%. Anodic and cathodic polarization behavior and corrosion rates were determined by the polarization resistance technique.Polarization scans showed that steel can exhibit activepassive behavior in both commercial-and reagent-grade CMA solutions. Reverse polarization scans indicated an unusual electrochemical behavior occurred with three current reversals in commercial-and reagent-grade CMA solutions of 2 wt% and higher. A current reversal occurred, followed by a cathodic loop; then a second current reversal occurred. An anodic current loop followed this second current reversal, which was in turn followed by third current reversal.The double-loop behavior was determined to be dependent on CMA concentration and upon the presence of carbon dioxide. It is proposed that carbon dioxide is formed as a consequence of an electrochemical reaction involving the acetate ion. The carbon dioxide dissolves in the solution and in turn results in precipitation of insoluble carbonates at cathodic sites on the steel surface. The total exchange current is lowered by the covering of cathodic sites and results in a shift in the corrosion potential in the cathodic direction. When the transient corrosion potential becomes more cathodic than the initial corrosion potential, then net anodic current will be drawn during the reverse anodic polarization scan. The double-loop behavior is then observed.KEY WORDS: calcium magnesium acetate, electrochemical behavior, steel INTR O D UCTI O NCalcium magnesium acetate (CMA) is a jargon name used to describe the reaction product of acetic acid and dolomitic limestone. This reaction product is a mixture of calcium acetate and magnesium acetate that has been identified as a possible replacement deicer for sodium chloride and calcium chloride deicers.' To develop an understanding of the electrochemical behavior and corrosivity of CMA to A36 (UNSt' ) K02600) steel, electrochemical testing was conducted in solutions of reagent-and commercial-grade CMA at concentrations of 0.5 to 20.0 wt%.In an earlier study by Luster, 2 electrochemical tests on steel

Effect of Alternative De-icers on the Corrosion Resistance of Reinforced Concrete Bridges and Highway Structures

“…This result is supported by a 4-year long study by Chollar, B. H. & Virmani, Y. P [24], which reported that after four years of ponding on reinforced concrete slabs with NaCl and CMA solutions, no corrosion was produced by the CMA solutions in contrast to the heavy corrosion and subsequent cracking of the concrete produced by the NaCl solutions. Similar conclusions were drawn by two studies that compared the electrochemical behaviour of metals immersed in solutions of various concentrations of CMA and NaCl [33,34]. In general, it can be said that CMA solutions do not induce corrosion of metals in almost any condition and in some cases even act as inhibitors.…”

Extractive Crystallization for the Production of Calcium Acetate and Magnesium Acetate from Carbonate Sources

“…Extensive research in the last 10-20 years has indicated that CMA has minimal or no detrimental effect on vegetation, aquatic life, water reservoirs, construction materials, and automobiles. [10][11][12][13][14][15][16][17][18][19] In an extensive study focusing on finding an alternative deicing material to sodium and calcium chlorides, only calcium acetate, magnesium acetate, and their combination were selected as the most competitive alternatives for replacing chloride deicing salts. 2,3,20 Any of the CMA forms would be an effective deicer for most geographical areas.…”