Study Of Electroplating Nickel Alloys On Mastoid Plates In Electrolyzer And The Pilotscale Experiment

With the continual utilization of fossil fuel,the shortage of energy has become increasingly severe,so research and development of the energy efficient and sustainable new secondary energy is of great significance.The hydrogen energy is extensively developed to solve this energy crisis.Hydrogen energy,being abundant,efficient,clean and renewable,is a potential energy carrier in future.Alkaline water electrolysis technology for hydrogen production,more mature,simple operation,is used to achieve large-scale hydrogen production.But corrosion in the environment of hot alkaline solution of dense concentration affects the sustainable,high efficient and stable operation of the water electrolysis cell.The thesis focused on the preparation of cathode connecting material(mastoid plates)in water electrolysis cell in order to prevent or reduce the galvanic corrosion between mastoid plates and the cathodes foam nickel/Ni-Mo.The Ni-Mo,Ni-W alloy coatings were electroplated on dark nickel-electroplated copper plates as substrates.Its aim was to prepare Fe/Ni/Ni-Mo,Fe/Ni/Ni-W with good corrosion resistance.The galvanic corrosion current density was lower when the alloy coatings were in touch with the foam nickel/Ni-Mo and the corrosion current density was also lower.Then Ni-Mo alloy electroplating process was used in the production of mastoid plates with a diameter of 830mm.The Ni-Mo alloys were electroplated on Fe/Ni as substrates.Optimum conditions and solution compositions were determined by single factor and orthogonal experiments.The results were as follows:60g·L-1 NiSO4·6H2O,20g·L-1 NiCl2·6H2O,80g L-1 Na3(C6H507)·2H2O,10g·L-1 Na2MoO4·2H2O,10g·L-1 NaCl,0.4g·L-1sccharin,0.5g·L-1 1,4-butynediol,0.05g·L-1 sodium dodecyl sulfate,60mL·L-1 NH3 H2O,temperature 50 ℃,pH 11,current density 2A·dm2,time lhour and the solution was stirred in medium speed.The electroplating coating prepared was bright,smooth,homogeneous and compact.In 30wt%KOH solution at 70 ℃,the galvanic corrosion current density of between Fe/Ni/Ni-Mo and the foam nickel/Ni-Mo and the potentiodynamic polarization curve of the Fe/Ni/Ni-Mo were measured.The galvanic corrosion current density was 10.9μA·cm-2 at 60min when the Fe/Ni/Ni-Mo prepared in the optimum conditions was in touch with the foam nickel/Ni-Mo.The corrosion current density of the Fe/Ni/Ni-Mo was 7.25 μA·cm-2.The surface morphology of the coating was observed by scanning electronic microscope.Results showed that,enlarging 2000 times,the coating surface was smooth,but there were local micro-cracks;enlarging 10000 times,there were large particles which were reunited and accumulated by large amounts of small granules.There were micro-cracks among large particles.EDS results showed that atom composition of the coating was Ni79.7Mo20.3.X-ray diffractometer was used to observe the coating phase.Results showed that the structure of coating was crystalline.The Ni-W alloys were electroplated on dark nickel-electroplated copper plates as substrates.Optimum conditions and solution compositions were determined by single factor and orthogonal experiments.The results were as follows:16g·L-1 NiSO4·6H2O,35g L-1 Na2WO4·2H20,40g·L-1 C6H807·H20,0.2g L-1 sccharin,0.5g L-11,4-butynediol,0.2g·L-1 sodium dodecyl sulfate,appropriate amount of NH3·H2O,temperature 65 ℃ pH 6,current density 5A dm-2,time lhour,and the solution was stirred in medium speed.The electroplating coating prepared was bright,smooth,homogeneous and compact.In 30wt%KOH solution at 70 ℃,the galvanic corrosion current density of between Fe/Ni/Ni-W and the foam nickel/Ni-Mo and the potentiodynamic polarization curve of the Fe/Ni/Ni-W were measured.The galvanic corrosion current density was 606μA cm-2 at 60min when the Fe/Ni/Ni-W prepared in the optimum conditions was in touch with the foam nickel/Ni-Mo.The corrosion current density of the Fe/Ni/Ni-W was 6.35μA cm-2.The surface morphology of the coating was observed by scanning electronic microscope.Results showed that,enlarging 2000 times,the coating surface was composed of many relatively uniform spherical particles,but there were local micro-cracks;enlarging 10000 times,the surface morphology was that a globular grain structure was reunited and piled into large spherical particle structure,large spherical particles accumulated was formed with some cracks.EDS results showed that atom composition of the coating was Ni81.6W18.4.X-ray diffractometer was used to observe the coating phase.Results showed that the structure of coating was crystalline.Ni-Mo alloy electroplating process was used in the production of mastoid plates with a diameter of 830mm.According to the design purpose and basis,the production workshop of mastoid plates was design.We amplified electrode assembly process,designed pilot process and used the swing arm and filter to replace the electromagnetic stirring experiment.Simultaneously,the selection of production equipment model and the workshop layout were completed.According to the characteristics of the process,electroplating power supply,exhaust fan and semi-automatic production line equipment parameters and brand also were selected.We completed the production of quality control standards and controlled the electrode production quality.We controlled the quality of the product by the pH value and the plating ion.And ultraviolet spectrophotometry was selected to detect the concentration of plating ions.The material of mastoid plates is dark nickel-electroplated steel.The mastoid plates were degreased by alcohol wiping and then painted with peelable protective colloid.The mastoid plates were degreased by immersing in mixed alkaline solution,activated as cathode,and then Ni-Mo alloys were electroplated at once.The coatings prepared were bright,smooth,homogeneous and compact.Eight Ni-Mo-electroplated mastoid plates,after tested,were transferred to the manufacturer of water electrolysis cell,examined and accepted.