Reduction of hexavalent chrome from artificial effluent of chrome: Batch electrocoagulation method [Reducción del cromo hexavalente de efluente artificial de cromado: Método de electrocoagulación por lotes]

The present research evaluated treatment time, electrode area / effluent volume ratio, on the% reduction of hexavalent chromium in artificial chrome plating effluents, was evaluated by the batch electrocoagulation method; Method for which A-36 steel anodes and cathodes of (5.0 x 5.0 x 0.2) cm were used. The number of electrodes and the separation between them was varied in order to vary the ratio of electrode area / effluent volume and; for a batch type electrocoagulation reactor in which 27 tests were carried out; keeping the volume of effluent treated constant. From the results obtained, it was determined that the increase in the electrocoagulation time and the electrode area / effluent volume ratio influence the percentage of hexavalent chromium reduction of the artificial chromium plating, as supported by ANOVA and test F; the maximum reduction percentage achieved was 91.65%, with respect to the initial concentration (20 mg/L), for a test time of 60 minutes and a ratio of electrode area / effluent volume of 0.912 m2/L.

Magnetite nanoparticles for reduction of hexavalent chrome in soil of an industrial park, Cerro Colorado - Arequipa [Nanopartículas de magnetita para reducción de cromo hexavalente en suelo de un parque industrial, Cerro Colorado – Arequipa]

One of the most important contamination problems in receiving bodies due to industrial activities is the presence of chromium (VI). One way to reduce the aggressiveness of said contaminant is its reduction to the form of chromium (III). The investigation determined the efficiency of magnetite nanoparticles in the treatment of soil contaminating with chromium (VI), to reduce it to chromium (III) of an Industrial Park at the district Cerro Colorado, province and department of Arequipa.22 samples of 1 kg of soil were taken, then homogenized according to the extraction distances, considering at the end only 3 samples called “Shore”, “6 Meters” and “9 Meters”, whose concentrations were: 146 mg / kg, 126 mg / kg and 67 mg / kg of Cr (VI) respectively. These samples were subjected to 3 treatments (T1, T2 and T3) with 3 repetitions each using 15, 30 and 45 grams doses of Magnetite nanoparticles for three weeks. At the end of the treatment using the EPA 3060 method, the Chrome (VI) analysis was performed. The 3 treatments “T1”, “T2” and “T3”, had significant differences for the final concentrations of Hexavalent Chromium in the soil; but it was in Treatment 3 in the soil samples "Shore", "6 Meters" and "9 Meters", where a greater effect was achieved in the reduction of Cr (VI) to Chromium (III) with an efficiency of 99.96%, 99.93% and 99.93% respectively, 45 grams of magnetite nanoparticles were used for this treatment.

ATMOSPHERIC CORROSION RESISTANCE OF TRIVALENT AND HEXAVALENT CHROME CONVERSION COATING ON ZINC ELECTRODEPOSITS IN HANOI AFTER 5 YEARS NATURAL EXPOSURE

In this paper, the corrosion resistances obtained after five year exposure of zinc coatings, trivalent chrome conversion coatings (CCCs) and hexavalent CCCs on zinc electroplatings are compared and discussed. The compositions of corrosion products of sample surfaces after exposure are investigated. The results of analysis by means of X-ray diffraction show that the corrosion products formed on zinc coatings, trivalent CCCs, hexavalent CCCs in atmospheric conditions of Hanoi have the distinctions specialty of the humid tropical climates. Zinc sulfate hydroxide hydrate Zn4SO4(OH)6.H2O; Zinc carbonate hydroxide hydrate Zn4CO3(OH)6.H2O; Simonkolleite Zn5(OH)8Cl2.H2O; Chromium Sulfate Cr2(SO4)3; Zinc chloride sulfate hydroxide hydrat Zn12(OH)15(SO4)3Cl3.H2O; Eskolaite Cr2O3 have been identified. The presence of SO2 results in the formation of Zinc sulfate hydroxide hydrate Zn4SO4(OH)6.H2O. After 5 years of exposure in atmospheric conditions, the hexavalent CCCs on zinc coatings have show the best corrosion resistance and the least corrosion products. The corrosion resistance of the samples decreases in the order: 747 > SP25 ~ TM 3108 > Zn.

Evaluation of Corrosion Performance of Zinc-Plated Underhood Automotive Fasteners Using Salt Spray Test

Mechanical fasteners such as screws, nuts, bolts, and washers are integral components in a vehicle. Rust or corrosion mechanisms of fasteners in the automotive industry is complex and may probably due to many factors includes temperature, pH, ion concentrations, coatings compositions as well as fastener geometry. Most of underhood fasteners used by PROTON models are Zinc coated fasteners. PROTON requires interior fasteners are coated to a minimum of 5 μm, while exterior fasteners are of 8 μm minimum thickness. There is a need to understand the corrosion performance of such fasteners in order to improve cosmetic and functional performances of these fasteners. The main objective of this study is to evaluate corrosion performance of three different compositions of Zinc-coated underhood fasteners using laboratory test. Samples were subjected to salt spray test with 5% NaCl for specific periods of time, in accordance ASTM B117-90 and JIS Z 2371:2000 conforming to their corrosion resistance requirements based on coating type and thickness. Results of the study revealed that Zn-Ni and Zinc-flake platings exhibit superior corrosion resistance characteristics with rating number (RN) of 10 compared to conventional 8 μm hexavalent-chrome free plated fasteners.