Corrosion Resistance Of Cu-14Al-X Coating By Supersonic Plasma Spraying

The new multiple aluminum bronze (Cu-14A1-X) alloy powder materials prepared by water-atomization technology were selected as the research object, the main composition of aluminum bronze alloy powders were Cu75～85%, Al12～16%, Fe2.0～4.0%, other alloying elements were Mn, Ni, Co, etc. In this paper, prepared a similar structure and properties of Cu-14Al-X coating samples using the technology of supersonic plasma spraying. Immersion test and electrochemical tests (Cyclic Voltammetry, Tafel technique, Open Circuit Potential and Electrochemical Impedance Spectroscopy) were adopted to characterize the corrosion resistance of coatings, when suitable test methods were found out, compared study them.Microstructure of the two Cu-14Al-X claddings were analyzed by means of metallographic microscope, electron probe micro analysis, X-ray diffraction and victor hardness tester. The results showed that different cladding technologies had obviously effects on microstructure, composition and hardness. Particles of supersonic plasma spraying cladding presented flat and were deformed sufficiently with few globular powders. Pointlike K phases distribute in the cladding which is uniform, compact and with clear laminar structure. While the structures of plasma cladding were bigger and more complex with dendritic and massive K phases. The hardness of supersonic plasma spraying cladding and plasma cladding were respectively360HV and260HV.The corrosion resistance of Cu-14Al-X coatings couldn’t be removed properly with immersion test because it was hard to decide which evaluation criteria, weight loss or weight gain, should be taken due to corroded products might be stuck in coatings with porous microstructure and were hard eliminated completely. Electrochemical tests have been considered to carry out the overall characterization of the corrosion resistance of Cu-14Al-X coatings properly, and more information such as corrosion potential, corrosion current and impedance could be obtained from the tests of Cyclic Voltammetry (CV), Tafel technique, Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS), which will enhance the further research on the corrosion behavior of coatings. And adopting continuous experiment detected the corrosion resistance of Cu-14A1-X coatings was feasible. As while as, continuous experiment could enhanced the further research on the corrosion behavior of coatings because it obtained more kinds of corrosion resistance datas on the same place of the same sample. Moreover, the results of CV, Tafel and EIS test could be confirmed with each other very well, and the results of immersion test and electrochemical tests could be confirmed with each other preferably.Different cladding process of Cu-14A1-X coatings had a great influence on the corrosion resistance. Through the comparison, that supersonic plasma spraying coatings corrosion resistance were better. Electrochemical experiments showed that Cu-14A1-X coatings in3.5%NaCl,5%H2SO4and10%NaOH solution happened off selective composition corrosion, which alloy coating surface of Al, Fe element due to low potential occuring respectively hydrogen depolarization corrosion reaction and oxygen depolarization corrosion reaction and priority corrosion. The corrosion rates in the three solutions in turn increase, respectively12.45,23.05and30.84mg·m-2-h-1. The results showed that two kinds of coatings in3.5%NaCl solution,5%H2SO4solution,10%NaOH solution had strong corrosion resistance. But corrosion resistance of the supersonic plasma spraying coatings in3.5%NaCl,5%H2SO4solution were better than the plasma spray welding layers, and electrochemical corrosion resistance increased obviously. At the same time, corrosion performance of the plasma spray welding layers in10%NaOH solution better than the supersonic plasma spraying coatings.