Защитные свойства Zr-содержащих конверсионных покрытий на цинке

The aim of the study is to develop an environmentally friendly chromium-free passivation technology for galvanized steel. Passivation of zinc coatings was carried out by deposition of conversion coatings from solutions containing ZrO(NO3)2, Na2SiF6 and oxidizer H2O2 or K2S2O8. The effect of the solution pH, the concentration of Na2SiF6 and the type of oxidizer on the protective properties of coatings was studied by the drop method and electrochemical method of linear voltammetry in 3 % NaCl using the full factor experiment 23 . The main effects and effects of the interaction of the studied factors for the darkening time of the droplet and the dissolution potential of zinc are calculated. The solution pH in the presence of the oxidizing agent K2S2O8 influences the both parameters in the most extent. Concentration of Na2SiF6 has a significant effect on the dissolution potential of zinc and the least effect on the darkening time of the droplet. An increase in the solution pH and the concentration of Na2SiF6 increases the protective properties of the coatings. Measurements of the mass loss and open circuit potential during the resource testing of conversion coatings in 3% NaCl showed an increase in the corrosion rate over time.Цель исследования − разработка экологически безопасной бесхромовой технологии пассивации гальванически оцинкованной стали. Пассивация гальванических цинковых покрытий проводилась осаждением на них конверсионных покрытий из растворов, содержащих ZrO(NO3)2, Na2SiF6 и окислитель H2O2 или K2S2O8. Изучалось влияние pH раствора, концентрации Na2SiF6 и типа окислителя на показатели защитных свойств покрытий методом капли и электрохимическим методом линейной вольтамперометрии в 3 %-ном NaCl с использованием полного факторного эксперимента 23 . Рассчитаны главные эффекты и эффекты взаимодействия исследованных факторов для времени потемнения капли и потенциала растворения цинка. Наибольшее влияние на оба показателя оказывает pH раствора в присутствии окислителя K2S2O8. Концентрация Na2SiF6 оказывает значительное влияние на потенциал растворения цинка и наименьшее влияние на время потемнения капли. Увеличение pH раствора и концентрации Na2SiF6 увеличивает показатели защитных свойств покрытий. Измерения потери массы и потенциала разомкнутой цепи в процессе ресурсных испытаний конверсионных покрытий в 3 %-ном NaCl показали возрастание скорости коррозии со временем

ИНГИБИТОРНАЯ ЗАЩИТА ОЦИНКОВАННОЙ СТАЛИ ВАНАДАТОМ НАТРИЯ

The results of investigation of corrosion inhibition of zinc-plated coatings in neutral chloride-containing corrosive medium by aqueous sodium vanadate solution are described. Investigations of corrosion inhibition of zinc-plated coatings on steel were performed by gravimetric and electrochemical method. The corrosive medium was neutral 3% sodium chloride solution, with a sodium vanadate concentration varied from 0.00005 M to 0.0003 M. Mass indices of corrosion, current density and corrosion potential of galvanized steel were determined depending on inhibitor concentration. Electrochemical studies show that the introduction of sodium vanadate in amounts of 0.00005–0.0003 M into the corrosive medium (3% sodium chloride solution) slows down the process of zinc corrosion. The corrosion process slows down by 3.3 times at an inhibitor concentration of 0.00005 M and by 20 times at an inhibitor concentration of 0.0002 M, respectively. An increase in the concentration of sodium vanadate to more than 0.0002 M is inappropriate, since an increase in the corrosion current occurs. The optimal corrosion inhibitor concentration for zinc-plated steel in 3% NaCl solution for Na3VO4 lies in the range of 0.0001–0.0002 М. The protection effect of the inhibitor found by gravimetric and electrochemical methods equals to 40–76% and 93–95%, respectively.  Описаны результаты исследования способа защиты гальванических цинковых покрытий в нейтральной хлоридсодержащей среде растворимым ингибитором коррозии ванадатом натрия Na3VO4. Исследования ингибиторной защиты гальванически оцинкованной стали Na3VO4 были проведены весовым и электрохимическим методами. Исследования проводили в 3%-ном растворе хлорида натрия в диапазоне концентраций ингибитора 0,0005–0,0003 М. Были определены массовые показатели коррозии, плотности тока и потенциалы коррозии оцинкованной стали в зависимости от концентрации ингибитора. Электрохимические исследования показывают, что введение в коррозионную среду (3% NaCl) в качестве ингибитора ванадата Na3VO4 в количествах 0,00005–0,0003 М замедляет процесс коррозии цинка. Процесс коррозии замедляется в 3,3 раза при концентрации ингибитора 0,00005 М, и в 20 раз при концентрации ингибитора 0,0002 М соответственно. Увеличение концентрации ванадата натрия более 0,0002 М нецелесообразно, так как происходит увеличение тока коррозии. На основании двух независимых методов исследования ингибиторной защиты оцинкованной стали ванадатом Na3VO4 можно сделать вывод, что оптимальная концентрация ингибитора коррозии Na3VO4 в 3%-ном растворе NaCl лежит в диапазоне 0,0001–0,0002 М. При этом защитный эффект ингибитора, определенный весовым методом, составляет 40–76%, а электрохимическим – 93–95%. 

Nickel pigments preparation by spent nickel-plating electrolyte precipitation

A way to recycle spent waste sulfuric acid nickel electrolytes by nickel compounds extracting is offered and in this paper. The nickel (II) ions con centration was defined by chemical analysis and solid phase composition were determined by elemental analysis. Slightly soluble nickel (II) compounds were precipitated with sodium hydroxide solution and satu-rated sodium orthophosphate solution during boiling. Also waste degreasing solution containing sodium hydroxide, sodium carbonate and sodium phosphate was used. Nickel (II) ions extraction degree for degreasing solution precipitation was 97%, and for sodium hydroxide solution or sodium orthophosphate solution precipitation – 99.9%. For nickel (II) compo unds obtained X-ray analysis, elemental analysis and thermal analysis were carried out, their IR-abs orption spectra micrographs were obtained. Colored compounds obtained from waste electrolytes had various shades of green colour scheme and high concentration of chromofore ions. That made them possible for pigments producing. The precipitates obtained were dried, calcinated, milled, sifted and then used as pigment compositions

Nickel pigments preparation by spent nickel-plating electrolyte precipitation

A way to recycle spent waste sulfuric acid nickel electrolytes by nickel compounds extracting is offered and in this paper. The nickel (II) ions con centration was defined by chemical analysis and solid phase composition were determined by elemental analysis. Slightly soluble nickel (II) compounds were precipitated with sodium hydroxide solution and satu-rated sodium orthophosphate solution during boiling. Also waste degreasing solution containing sodium hydroxide, sodium carbonate and sodium phosphate was used. Nickel (II) ions extraction degree for degreasing solution precipitation was 97%, and for sodium hydroxide solution or sodium orthophosphate solution precipitation – 99.9%. For nickel (II) compo unds obtained X-ray analysis, elemental analysis and thermal analysis were carried out, their IR-abs orption spectra micrographs were obtained. Colored compounds obtained from waste electrolytes had various shades of green colour scheme and high concentration of chromofore ions. That made them possible for pigments producing. The precipitates obtained were dried, calcinated, milled, sifted and then used as pigment compositions

Analysis of corrosive properties of zinc-containing coatings based on dispersed waste hot zinc plating

A comparative analysis of the corrosion properties of zinc-containing coatings obtained on the basis of metallic powder zinc and dispersed hot-dip galvanized waste has been carried out. The results of a study of the corrosion resistance of zinc-containing coatings by the electrochemical method and in a salt spray chamber have shown that coatings obtained on the basis of dispersed hot-dip galvanized waste are not inferior in protective properties to coatings based on powder standard zinc