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.

The corrosion of metal surfaces causes huge financial damages to the industries annually, what has lead to an increase in the search for substances that can slow down or prevent corrosion rate. Green inhibitors which are biodegradable, without any heavy metals and other toxic compounds, are promoted. Amino acids are attractive as corrosion inhibitors because they are nontoxic. We have used methionine as corrosion inhibitor. Materials under investigation are two kind of low allow carbon steel marked as: Steel 39, Steel 44 usually applied to concrete as reinforcing bars, and manufacture in Elbasan. The inhibition effect of methionine on the corrosion behavior of low allow steel is investigated in sulfuric acid in presence of chloride ions, in form of NaCl (H 2 SO 4 1M + Cl -10 -3 M). Potentiodynamic polarization method is used for inhibitor efficiency testing. The pitting corrosion current shows that increasing concentration of the inhibitor causes a decrease in pitting current density, and inhibition efficiency increases with increasing concentration of the inhibitors.

The use of green inhibitors as environmentally safe corrosion inhibitors for metal and alloys has, in recent times, received attention from researches. The extract of pineapple crown was studied as an inhibitor in 1M H 2 SO 4 and 1 M HCl, with different concentration of pineapple extract, for iron B 500. The corrosion inhibition efficiency was investigated by using the weight loss method. The inhibition efficiency increases with the increase of the inhibitor concentration to attain 98.1 % at 4 g/L of pineapple crown extract. Based on the obtained results, pineapple crown extract reacts as a good inhibitor in aggressive media.

The development of green corrosion inhibitors are highly demanded because of the increasing demand of green chemistry in the area of science and technology. Use of plant extracts as corrosion inhibitors has attracted significantly attention. The present study investigates corrosion inhibition of pineapple crown extract for steel 39 in 1M H₂SO 4 and 1M HCl. The weight loss method is used for inhibitor efficiency testing. The inhibition efficiency of inhibitor increases with the increases of concentration of inhibitor. Use of this inhibitor in concentration 3g/L present protection efficiency 82.88 % for steel 39 in aggressive media. The results present that pineapple crown extract is a good choice for steel 39 and environment, too.

The durability degradation of reinforced concrete structures is one of the biggest problems hindering the breakthrough in engineering and has attracted a great deal of attention in the field of civil engineering. Corrosion issues of internal steel reinforcement have become a top priority in durability treatment since they seriously threaten the durability and sustainability of the structure. Migrating corrosion inhibitors (MCIs) are a good alternative to prevent or control reinforcing steel corrosion because of their moderate cost and easy application compared with other preventive methods. Our study concerns the investigation of the protective effect of MCI; different concentrations of butanol-1 amin-2 refer 1g/L lysine. Materials under investigation are two kind of low allow carbon steel marked as: Steel 39, Steel 44. The corrosion media is sulfuric acid in presence of chloride ions, in form of NaCl (H2SO4 1M + Cl -10 -3 M). Potentiodynamic polarization method is used for inhibitor efficiency testing. Potentiodynamic polarization measurements showed that the presence of MCI in acidic solution decreases the corrosion current to a good extent. Use of this inhibitor in concentration 12 g/L butanol-1 amin-2 with 1g/L lysine, referring the corrosion protection of steel 39 presents protection efficiency 90.52% and for steel 44 present protection efficiency 75.98% classifieds as good for this extreme aggressive conditions.