In response to market feedback on rust problems,through analysis of rusted components,the research topic was determined to be the thickness of the electrophoresis inner cavity of the side beam,and the four electrochemical reactions involved in electrophoresis,electrophoresis,electrodeposition,and electroosmosis were identified and analyzed during the electrophoretic film formation process.Identify the key parameters that affect electrophoresis film formation,such as voltage,bath temperature,electrophoresis time,cathode-to-anode area ratio,solvent content,etc.,and perform parameter analysis,DOE test,and actual production verification on the production line.The solvent content is 0.70%and the temperature is 31°C,electrophoresis voltage under the condition of 320 V,the minimum value of the inner cavity film thickness of the side beam is increased from 6.0μm to 10.8μm,which meets the anti-corrosion requirements of the product.