Lysine as corrosion inhibitor for low alloy carbon steel in acidic media

Abstract

The use of inhibitors is one of the most practical means for protecting metals against corrosion, especially in acidic media. The interest is to use organic compounds as inhibitors due mainly to their inherent and non-toxic nature. Amino acids are attractive as corrosion inhibitors because they are nontoxic, relatively easy to produce with high purity at low cost, and are soluble in aqueous media. Lysine, one kind of amino acid is used as inhibitor. The aims of this study are to show corrosion protection efficiency of lysine and to explain the mechanism of corrosion. The experimental results demonstrated that the lysine offered protection for low alloy carbon steel in aggressive environments like H 2 SO 4 . Materials under investigation are two types of low alloy carbon steel marked as: Steel 39, Steel 44 (usually applied to concrete as reinforcing bars). The corrosion media consists in sulfuric acid in presence of chloride ions, in form of NaCl (H 2 SO 4 1M + Cl -10 -3 M). Potentiodynamic polarization methods are used for inhibitor efficiency testing. Potentiodymanic polarization measurements showed that the presence of lysine in acidic solution decreases the corrosion current to a good extent. The corrosion inhibition efficiency improves with the increase of the lysine concentration. The use of this inhibitor (1g/L) protects steel 39 in acidic media with 78.88% efficiency. That means lysine is a good corrosion inhibitor for these aggressive conditions.

Effects of Migrating Inhibitors on Corrosion of Reinforcing Steel in Aggressive Environment

“…The examination of figure 2 -aand figure 3 -a-shows that the MIC (mix of amino-alcohol and lysine) functioned via a mixed-inhibition mechanism; it worked as well as anodic and cathodic inhibitor. The (amino-alcohol), as migrator agent, seems to play an important role in specifying the areas of anodic adsorption of inhibitor (the rest potential become more positive increasing the concentration of amino-alcohol) and improve the anodic surface coverage (anodic branch come down increasing the concentration of amino-alcohol) (12,13). Clearly the presence of amino-alcohol as migrator agent improves the inhibition effect of lysine, even in low concentration.…”

The inhibition effects of methionine on mild steel in acidic media

“…1 and the methionine structure in Fig.2. Prior measurement, the steel samples are polished with different emery paper, rinsed with double distilled water and dried in air [6,7,8]. The measurements were conducted in 1.0 M sulfuric acid + 10 -3 Cl -solutions at the following methionine corrosion inhibitor concentrations: 0.25g/L, 0.5g/L, 0.75g/L and 1g/L.…”

“…Corrosion current density was determined using the cutting point of Tafel extrapolation line and v corr was calculated according to Faraday's law [7,10] (1) (1) where a represents the atomic weight of the metal (a=56 g/mol), i -corrosion current density in (µA/cm 2 ), n -the number of electrons exchanged during metal dissolution (n=2), D -the density in (g/cm 3 ) (D=7.86 g/cm 3 ) and K is a constant which equals to 0.00327 if corrosion rate (V corr ) is calculated in [mm/y] [8].…”