Evaluation of porosity of chromecarbide coatings on different classes of structural materials using measurement of systems stationary potential
Stationary potentials of pyrolytic chromecarbide coating (PCCC), deposited on samples of various structural materials, like steel 30HGSA, titanium alloy VT6 and aluminum alloy D16ch.-T have been measured in 3% aqueous NaCl solution. Thickness of chromecarbide coatings ranged from 6 to 30 μm. In order to eliminate the influence of substrate on formation of stationary potential the PCCC was deposited on glass samples. The potential steady-stated in 72 hours was taken as stationary. Additionally to coated samples the initial samples of selected structural alloys were studied. Research has shown that PCCC is a cathode coating and the value of its stationary potential is +285 mV. Stationary potentials of the used structural materials have negative values, which range from -110 to -730 mV. Analysis of experimental data showed that the decrease in thickness of coating leads to a shift of the value of stationary potential to negative range, i. e. at small coating thicknesses substrate through the pores in the coating has an impact on formation of system stationary potential. Work is executed within implementation of the complex scientific direction 17.1 «Ecologically safe, plasma electrolytic coatings for light alloys» («The strategic directions of development of materials and technologies of their processing for the period till 2030») [1].