Study On The Codeposition Process And Properties Of Electrodeposited Ni-Fe-Cr Alloy Coating On Polyurethane Foam

Ni-Fe-Cr alloy coating was prepared on the surface of porous polyurethane foam by co deposition.The performances of porous foam alloy materials combine with the open pore structure of polyurethane foam and excellent performances of Ni-Fe-Cr alloy,such as high specific surface area,high porosity,good mechanical strength,corrosion resistance,high-temperature oxidation resistance and thermal shock resistance.The effects of different factors,such as temperature and pH value of solutions and cathode current density on the deposition rate,hydrogen evolution reaction and density ratio were studied during the metal(Ni or Cr)deposited on the surface of porous polyurethane foam.The results indicated that the maximum deposition rate of metal Ni deposited on the surface of polyurethane foam could reach 36.91 mg cm-2 h-1;Cr deposited on the surface of porous Ni foam,the maximum deposition rate was only 0.4990 mg cm-2 h-1.The control factors of the hydrogen evolution reaction,the internal stress and the density of the metal coating(Ni or Cr)under the three-dimensional network structure were discussed.The maximum relative density of the porous Ni foam is 60.07%,and the relative density of the porous Cr foam is only 28.52%.Ni-Cr,Ni-Fe and Fe-Cr alloy coatings were prepared on the surface of porous Ni foams by direct current electrodeposition.The effects of temperature,pH value and cathode current density on the thickness,deposition rate,the compositions and pattern of the coatings were investigated.The high-temperature oxidation and thermal shock performances of the porous bimetallic foams materials were also tested.The results showed that porous Ni foam adding Cr element improved the high-temperature oxidation resistance of the materials,adding Fe element made that the surface of Ni-Fe coating was composed of spherical particles arranged closely.This structure made the porous Ni-Fe alloy foam material with good thermal shock resistance.The electrochemical behaviour was studied during the process of co deposition of Ni-Fe-Cr alloy on the face of porous Ni foams.The conclusions were that the plating solution components,such as stabilizer,brightener and conductive additives could effectively improve the dispersion of solution,reduce the the potential of hydrogen evolution reaction and raise the current efficiency.After adding metal ions,the hydrogen evolution potential was increased.The process of co deposition of Ni-Fe-Cr alloy mixed with hydrogen evolution reaction and the current efficiency reduced.The results of cyclic voltammetry curve and cathodic polarization curve showed that the order of deposition rate of the three elements was Ni>Fe>Cr in the plating solution of co deposition of Ni-Fe-Cr alloy on the surface of porous Ni foams.The apparent activation energy of reaction under the different deposition potentials was calculated according to cathodic polarization curves.The electrochemical reaction was the control step when the apparent activation energy was more than 40 kJ mol-1 under the co deposition potential of Ni-Fe-Cr alloy.The influence of experimental parameters on thickness,deposition rate and compositions of Ni-Fe-Cr alloy coating prepared by direct current co deposition were studied systematically.The relationship between the plating solutions and compositions of coatings was discussed.The contents of Ni-Fe-Cr alloy coating were Cr 21.2%,Fe 43.9%and Ni 34.9%respectively.The porous ternary metal foam was a polyhedron structure with irregular pentagonal.The skeleton configuration was three prism scattered bulge with small grains,and its cross section was "triangle" tubular structure.The surface of Ni-Fe-Cr alloy coating was composed of densely arranged spherical particles under the conditions that the concentration of CrCl3·6H2O was 160 g/L,the concentration of FeCl2·4H2O was 9 g/L,the temperature of plating solution was 30 ℃ the cathode current density is 24.0 A dm-2 and pH value of plating solution was 2.0 for half an hour.The coating has no impurity and high purity.The high-temperature oxidation and thermal shock performances of porous Ni-Fe-Cr alloy foam materials were tested.The results were that the ternary metal foam materials(Cr:20.3%～21.4%;Fe:43.2%～44.4%;Ni:34.5%～36.0%)had good thermal shock resistance.When the Cr content of ternary metal coating was more than 12.7%,the porous Ni-Fe-Cr alloy foam material had resisted to high-temperature oxidation.And the higher the Cr content was,the better this material had the high-temperature oxidation resistance.