The effect of Zinc, Tin, and Lead coating on corrosion protective effectiveness of steel reinforcement in concrete

Abstract

The research was aimed at developing new reinforcement materials by using of different coating materials, included zinc, tin and lead. The experimental works included examination of coating defect, coating Adhesion study, and the adhesion between concrete and coated bars, and different techniques are employed to assess the performance of the reinforcement embedded in concrete at a saline environment of 3.5% NaCl solution. These include; Accelerated Corrosion Test ASTM G 109, Half Cell Potential Test ASTM C876, electrochemical polarization by Linear and Tafel polarization techniques, microstructure, and visual inspection. Some improvement to the ASTM G109 standard test method were suggested and led to get more useful results in a shorter period. The trend of the corrosion rate results of the all specimens (worst-to-best) can be arranged as follows: Galvanized CRS › untreated CRS› tin coated CRS › lead coated CRS › SST316

Evaluation of corrosion resistance of coated steel strips embedded in mortar under chloride exposure

“…It acts as a barrier preventing access of oxygen and moisture to the coated steel and it acts as a sacrificial anode which corrodes protecting steel which becomes the cathode. The performance of zinc-coated (galvanized) steel reinforcement against corrosion under chloride exposures is widely reported in literature (Molina et al, 1984;Rasheeduzzafar et al, 1992;Maldonado and Pech-Canul, 2006;Bellezze et al, 2006;Ann and Song, 2007;Darwin et al, 2009;Maldonado, 2009;Alsamuraee and Ameen, 2011). The CTL value for galvanized steel has been reported to be 2 to 2.5 times the CTL value for unprotected steel (Maldonado and Pech-Canul, 2006).…”

“…Coating of steel reinforcement is considered when the structure is to be exposed to moderately or highly corrosive conditions. Durability of coating, easy applicability of coating in field or plant, resistance of coating against damage during transport, the bond of coating with steel and concrete, bendability of coated bars are the requirements for good performance of coatings against corrosion (Alsamuraee and Ameen, 2011). Two major categories of coatings applied on steel reinforcement for corrosion protection are: metallic and non-metallic coatings.…”

“…When a Portland cement is well-hydrated, it results into formation of calcium hydroxide in the range of 15 to 30 per cent by mass of the dry cement. In the presence of calcium hydroxide in the pore water, an alkaline environment having pH of 12 to 13 is created around the steel (Alsamuraee and Ameen, 2011). Due to the high pH around the steel, a protective layer of ferric oxide is formed on the steel surface which limits the access of moisture and oxygen to the steel, reducing the solubility of iron.…”

“…This process is called as passivation of steel against corrosion. However, the immunity of steel against corrosion is lost and corrosion of steel is initiated once the passive layer is destroyed either by lowering the pH due to carbonation or by penetration of chloride ions into the passive layer or by both (Darwin et al, 2009;Alsamuraee and Ameen, 2011).…”

“…TI values can be increased by increasing CTL value and cover thickness. Improving quality of concrete and applying concrete surface coatings which can reduce the rate of chloride diffusion through the cover concrete would further increase the TI (Babaei and Hawkins, 1987;Ann and Song, 2007;Darwin et al, 2009;Cusson and Qian, 2009;Alsamuraee and Ameen, 2011). Coating of steel reinforcement is considered when the structure is to be exposed to moderately or highly corrosive conditions.…”