Abstract:Electrochemical

The effect of added carbon black to concrete mix on corrosion of steel reinforcement was studied. This was achieved by inserting steel bars in different concrete mixes containing 0.1, 0.2, 0.3, 0.4, and 0.5, carbon black/cement. Samples were cured, immersed in 3.5% chloride solution for 6 months. Chloride permeability and corrosion rates were measured. Tests showed that corrosion rate and chloride ions penetration decreased with increased carbon black content. This was expressed due to filling effect of very fine particles of carbon black and was in the order less than 250 nm.

The present study explores a new method of steel particle-reinforced copper matrix composite synthesis. Steel reinforced copper was prepared by stir casting processing method at variable percentages between 10 wt% and 50 wt%. Characterization and mechanical testing were performed on these composites using a variety of techniques. The results showed that the microstructure of the composites has a uniform distribution of steel particles in the matrix with good interfacial integrity. Brinell hardness, tensile and yield strengths, impact energy and compressive yield strength of the composites increased with increasing steel particle contents. Vickers micro-hardness increased markedly at the interface region between particle and matrix evident by the hardness maps. The friction coefficient increased proportionally with increasing steel particle content in the composite, but the contrary was noticed for accumulative wear amount. A slight decrease in deformability is expected by increasing particle content. A ductile fracture was noticed in fractographs of fracture surfaces. Cracks are propagated in the Cu matrix up to the point of fracture, i.e. not through the interfacial boundaries.

Durability of concrete structures decrease due to corrosion in structures exposed to corrosive conditions. Several methods are adopted to minimize corrosion of steel in concrete; one of the methods is the use of inhibitors. In this work, the effect of inhibitor addition on corrosion of steel in concrete was investigated. Inhibitors added to concrete mix in different ratios, samples then immersed in 3.5% NaCl, and in Dead Sea Water for 15 months. Potential of steel reinforcement was measured by copper sulfate electrode according to ASTM C876. Results showed that an addition of 2% calcium nitrate or more was acceptable for adequate protection.

Steel reinforcements of 8 mm diameter and 24 cm length were cut from steel and after pickling treatment of all specimens. Steel reinforcements then were galvanized by hot dipping method. The measured coating thickness by thickness gage meter of zinc coat was in the range 8 -11 µm. Bare steel samples were also used for comparison reasons. Each steel bar was inserted in a middle of a plastic tube with 4.5 cm diameter into which concrete was cast. After proper curing, specimens were immersed into 3.5% NaCl and Dead Sea water separately. Electrochemical impedance spectroscopy measurements were performed at different time intervals. Results showed that galvanized steel was corrosion resistant in sea water, and Dead Sea water over the test period.