Corrosion of iron by ascorbic acid and catalysis of ascorbate oxidation by products of the iron corrosion

Abstract

Electrolytic iron (99.8% Fe) prepared as small plates was exposed to oxygenated solutions of ascorbic acid. Gravimetric corrosion rates and ascorbate oxidation rates were measured simultaneously in a new apparatus designed for that purpose. The mean corrosion rate was high for iron in 1 mM ascorbic acid at 365 mdd (mg dm-2 day-1) (6-h tests, n = 12) and was highly dependent upon ascorbate concentration, increasing to 3200 mdd in 11 mM ascorbic acid. Corrosion of iron in oxygenated, deionized water was zero for these tests. Ascorbic acid oxidation under these oxygenated conditions agreed well with the first-order rate model. Ascorbate oxidation proceeded slowly in the absence of iron. Mean kx (first-order rate constant) was increased 4-5 times by the presence of an elemental iron plate in the solution and 10 times by the addition of fine electrolytic iron powder (99.9% Fe). In these nonbuffered solutions, the ascorbate oxidation rate was unchanged when iron corrosion from plates was doubled or tripled in the solutions. High concentrations of iron powder in the solutions did not cause higher rates of ascorbate oxidation than small amounts of iron. Nutritional and food processing implications of these results are discussed.

Causes of Severe Magnetite Formation During Underbalanced Drilling and Practical Mitigation Strategies

“…Within the food and drug industry, it has been noted that ascorbic acid (Vitamin C) can increase the rate of iron corrosion and its subsequent dissolution into an aqueous media (Rosanoff et al 1985;Valek et al 2008). With that in mind, the employed oxygen scavenger was sodium erythorbate, a stereoisomer of sodium ascorbate.…”