Electroplating of zinc and tin alloys with nickel and cobalt from ammonium oxalate electrolytes
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 7, pp. 1272—1278, July, 2020
Electroplating of zinc and tin alloys with nickel and cobalt from ammonium oxalate electrolytes* K. A. Kamysheva, R. F. Shekhanov, S. N. Gridchin, and A. V. Balmasov Ivanovo State University of Chemistry and Technology, 7 Sheremetevsky prosp., 153000 Ivanovo, Russian Federation. E-mail: [email protected] A possibility of preparing good quality electrolytic alloys zinc-nickel, zinc-cobalt, tinnickel, and tin-cobalt from ammonium oxalate electrolytes of various compositions was shown. The alloy coatings of high quality can be obtained at the current density range from 1 to 3 A dm–2. The introduction into the electrolyte of ammonium oxalate capable of forming stable complexes with Zn2+, Sn2+, Ni2+, and Co2+ ions makes it possible to increase the working pH range. Electroplating occurs with high cathodic polarization favoring the formation of qualitative finely crystalline coatings of the plated alloys. Key words: electrolytic alloys, polarization experiments, protective coatings, electroplating, corrosion resistance.
Galvanized zinc, cadmium, or tin coatings are traditionally used to protect black metals from corrosion. The introduction of the iron subgroup metals (iron, cobalt, and nickel) into the composition of anticorrosion coatings makes it possible to substantially elongate their protective period, because the corresponding binary alloys are characterized by a higher corrosion resistance than the indicated individual metals.1 The use of compounds forming soluble complexes with ions of the plating metals is a promising trend for the development of new compositions of electrolytes for the electroplating of metals and alloys.2—18 One of the most efficient complexing components of the electrolyte is ammonium oxalate, whose advantage is the possibility of decomposing the formed complexes in wastewater. We earlier demonstrated the efficiency of application of ammonium oxalate for the stabilization of the electrolyte when manufacturing electrolytic coatings by the iron subgroup metals.14—17 The purpose of this work is to study electroplating of zinc-nickel, zinc-cobalt, tin-nickel, and tin-cobalt alloys from the ammonium oxalate electrolytes. Experimental Solutions of electrolytes were prepared from the analytical purity grade reagents. Each component of the electrolyte was dissolved in distilled water in a separate vessel, each solution was filtered, and the filtered solutions were combined in a common
* Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
vessel. The acidity of the solution was corrected by the addition of a 25 or a 50% aqueous solution of sulfuric acid. The coatings were plated with an MPS-3005L-3 Matrix laboratory current source on the preliminarily prepared (degreased and activated) samples of the 08kp steel. Electroplating was carried out at 20—50 С and a cathodic current density of 1—3 A dm–2. The quality of the coating
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