Jhon Jairo Olaya Florez

Steel corrosion assessment by electrochemical impedance on metakaolin blended mortars

Since Corrosion of reinforcing steel in concrete is the cause of major economic losses, Portland cement has been traditionally replaced by cements blended with pozzalanic materials, most of which have been found to reduce the corrosion of steel. This paper shows the results of an experimental research aimed to investigate the corrosion of reinforcement in mortar using electrochemical impedance spectroscopy (EIS). For this, concrete laboratory samples containing a 0.0055 m steel bar and prepared with just ordinary Portland cement (OPC) and metakaolin at a replacement level of 20% were analyzed. In order to accelerate the steel corrosion process, all the samples were kept in a 3% NaCl solution and a constant anodic electrical potential was applied. Variations in the water to cementitious material ratio (0.5 and 0.6) and metakaolin proportion were analyzed, while the cementitious material to sand ratio was kept constant at 1:2.25 in all of the specimens. The results showed a reduction in corrosion rates when metakaolin was used as a blending admixture, especially at water to cementitious material ratio of 0.5.

Resistencia a la corrosión de recubrimientos de NbC sobre acero AISI 316L depositados por UMB

In this work NbC coatings were deposited on AISI 316L steel substrates by reactive unbalanced magnetron sputtering. The coatings were deposited at room temperature to avoid heating alterations in the steel substrate microstructure, without bias and with a thickness of 200 nm. The coatings microstructure was characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Adherence of the coatings was evaluated using the scratch test and its corrosion resistance was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results indicate that the coating NbC has (111) preferential orientation, exhibits good adhesion and has good corrosion resistance for stainless steels protection.

Electric arc spray coatings for the naval industry

Carbon and stainless steel, as well as Fe-Nb-Cr-W coatings were deposited on steel substrates by using electric arc spray, and its possibility of applying such coatings in the naval industry was analyzed. In order to achieve this, the coating microstructure was characterized before and after the corrosion, abrasive wear, and thermal barrier tests. Corrosion resistance was analyzed via potenciodynamic polarization test using a NaCl electrolyte at 3%; abrasive wear resistance was measured by using a three-component system following ASTM G-65 recommendations, while quality control as thermal barriers was studied by using EIS tests. Scanning Electron Microscopy, optical microscopy and X-ray diffraction were used to characterize the microstructure of the coatings.