Induced Co-deposition of Co-Fe Alloy on Silicon Steel Surface
Most scholars have investigated silicon steel coated with an insulating varnish and a magnesium silicate substrate covering the surface of silicon steel.However,before silicon steel is coated with an insulating varnish,it is exposed to an uncontrolled environment,which significantly increases the risk of corrosion.Therefore,investigating processes that enhance the corrosion resistance of silicon steel without affecting its soft magnetic properties is crucial.In this study,the process of preparing Co-Fe soft magnetic alloy plating by induced co-deposition on the surface of silicon steel is proposed to address the problems of corrosion resistance and soft magnetic properties of silicon steel.In addition,sodium saccharin(C7H8NNaO4S)is a commonly used additive in the plating process of sodium saccharin in the sulfur element;although the content of a very small amount of the plating layer and its soft magnetic properties have a negative impact,non-toxic and non-polluting sodium tartrate,instead of sodium saccharin,was used in this study.After preparing the Co-Fe soft magnetic alloy coating,the microstructure of the coating and change of elemental content were studied in detail using scanning electron microscopy and energy dispersive spectroscopy;the phase structure composition of the coating and peak diffraction intensity were analyzed using X-ray diffraction;and the soft magnetic properties were investigated using the hysteresis line measured by vibrating-sample magnetometry.The process parameters such as cobalt sulfate concentration,deposition current density,pH,and sodium tartrate concentration were optimized step by step by the above test methods,and the optimal process parameters were selected and the optimal coating structure was constructed by analyzing the microstructure of the plating layer and the variation of the elemental content of the plating layer.The results show that the optimum process parameters are 20 g·L-1 cobalt sulfate,45 g·L-1 sodium tartrate,pH=8,and 0.3 A·cm-2 current density,and the plated layer has a dense morphology and uniform grain distribution.In addition,the phase structure of the plated layer was Co7Fe3 with no significant difference in the preferred orientation for each process parameter.Cobalt content that is excessively high or low in the coating has a negative effect on the soft magnetic properties;when the cobalt content reaches 65.11％,the saturation magnetization strength reaches 209 emu·g-1((A·m2)/kg),the coercivity is below 4 Oe(1 Oe=79.6 A/m),and the plating has optimal soft magnetic properties,which meets the national requirements of the soft magnetic properties of silicon steel.In the corrosion test,the corrosion solution used in previous studies was a NaCl solution with a mass fraction of 3.5％,but the working environment of the silicon steel of the transformer core was exposed to air or was in a harsh acidic environment.Therefore,the corrosion solution we selected was a vented acidic solution(HC1)with pH 3,4,and 5,and vented deionized water,to simulate the actual production and storage environment and to ensure that the oxygen was saturated.The test studies on corrosion performance revealed that the corrosion potential of cobalt-iron alloy plating was positively shifted by 0.012 V and the self-corrosion current density was reduced to 2.86 μA·cm-2 in pH=5 acidic solutions,which provided more optimized corrosion resistance.Compared with the traditional silicon steel surface coating,insulating varnish,and magnesium silicate substrate research,the electrodeposition of Co-Fe soft magnetic alloy is a new type of protection method,and the future surface treatment of silicon steel has reference significance.
silicon steelinduced co-depositioncobalt-iron alloysoft magnetic propertiescorrosion protection
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