effect of the type of surface treatment and cement on the chloride induced corrosion of galvanized reinforcements

The effect of a new passivation treatment, obtained by immersion of the galvanized reinforcements in a trivalent chromium salts based solution, on the chlorides induced corrosion has been investigated. To investigate also the effect of cement alkalinity on corrosion behaviour of reinforcements, concretes manufactured with three different European cements were compared. The obtained results show that the alternative treatment based on hexavalent chromium-free baths forms effective protection layers on the galvanized rebar surfaces. The higher corrosion rates of zinc coating in concrete manufactured with Portland cement compared to those recorded for bars in concrete manufactured with pozzolanic cement depends strongly on the higher chloride content at the steel concrete interface

Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation

The performance of a one- and two-compartment electrochemical reactor under galvanostatic control for zinc recovery present in the spent pickling solutions is studied in this paper. These solutions, which mainly contain ZnCl 2 and FeCl 2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the anion-exchange membrane (AEM) on the figures of merit of the electrochemical reactor is analyzed. In the absence of iron in solution, as the current value was shifted towards more negative values, the zinc fractional conversion increased because of the increase in the zinc reduction rate. However, the increase in current values made current efficiency decrease due to the hydrogen-reduction side reaction, which caused an increment in the specific energy consumption. The presence of iron in synthetic solutions led to a decrease in current efficiency associated with the reverse redox Fe 2+/Fe 3+ system and to the enhancement of the HER, which also induced increments in the local pH and the subsequent zinc redissolution. These adverse effects related to the presence of iron could be minimized by the interposition of an AEM. In this case, the zinc redissolution was eliminated which enabled zinc conversion values close to 100% together with higher current efficiencies as the consumption of current by the system Fe 2+/Fe 3+ was diminished. © 2012 Elsevier B.V. All rights reserved.Authors want to express their gratitude to the Universidad Politecnica de Valencia for the economic support in the Project Reference PAID-06-08, and to the Generalitat Valenciana for the financing of the Project Reference GV/2010/029.Carrillo Abad, J.; García Gabaldón, M.; Ortega Navarro, EM.; Pérez-Herranz, V. (2012). Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation. Separation and Purification Technology. 98:366-374. https://doi.org/10.1016/j.seppur.2012.08.006S3663749

Electrodeposition of nickel-zinc alloy from a sulfamate bath

The electrodeposition of Ni-Zn alloy coatings having high nickel content (74-97 wt%) from a sulfamate bath was studied. The investigation was performed by means of cyclic voltammetry, potentiostatic electrodeposition, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The effect of the experimental parameters (deposition potential, zinc concentration, addition of sodiumdodecylsulphate) on the coating composition, morphology and structure was studied. The obtained results show that the addition of Zn2+ to the deposition bath leads to a strong decrease in the cathodic current density, indicating a remarkable inhibition of Ni reduction. Even if anomalous codeposition was observed for all the studied experimental conditions, nickel rich alloys were obtained due to the mass transport control. A sudden decrease in the current efficiency, indicating a decrease in the hydrogen overvoltage, was found on increasing zinc percentage in the alloy over than about 15 wt%. The incorporation of Zn in the cfc Ni lattice up to about 20 wt% leads to a grain refinement and to an increase in hardness