Impedance spectroscopy studies of electroless Ni–P matrix,Ni–W–P,Ni–P–ZrO2, and Ni–W–P–ZrO2 coatings exposed to 3.5% NaCl solution |
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Authors: | A. Stankiewicz J. Masalski B. Szczygieł |
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Affiliation: | 1. Department of Inorganic Chemistry, Wroc?aw University of Economics, ul. Komandorska 118/120, 53‐345 Wroc?aw (Poland);2. Faculty of Chemistry, Wroc?aw University of Technology, Wybrze?e Wyspiańskiego 27, 50‐370 Wroc?aw (Poland) |
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Abstract: | Ni–P matrix, ternary Ni–W–P and Ni–P–ZrO2 coatings, and quaternary Ni–W–P–ZrO2 coatings were deposited using electroless method from a glycine bath. Their corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) for various immersion times in a 3.5% NaCl solution. From among the investigated coatings, the ternary Ni–W–P coatings show the highest resistance to corrosion in the first hour of exposure to the 3.5% NaCl medium. An addition of ZrO2 adversely affects the performance of both the Ni–P coatings and the Ni–W–P coatings. For all the coatings, including the ones containing tungsten, a marked decrease in pore resistance (Rpor) over time is observed. This means that their corrosion resistance and capacity to protect the substrate decline. On the other hand, after 24 h immersion in the 3.5% NaCl solution the Ni–W–P coating shows the highest low‐frequency impedance modulus (|Z|f = 0.01 Hz). As regards corrosion resistance, the Ni–P coatings and the Ni–W–P coatings perform best. |
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Keywords: | composite coating corrosion resistance EIS electroless plating Ni– P |
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