Liquid phase corrosion test is the core method for evaluating the rust prevention performance of media such as oil and water,Liquid phase corroded steel rodAs the core carrier of the experiment, the rationality of its selection and the standardization of preprocessing directly determine the accuracy, repeatability, and comparability of the experimental results. The following provides a detailed explanation from two aspects: selection principles and preprocessing requirements.

The selection of steel bars must strictly follow the principles of test standards and medium compatibility. In terms of material, high-quality carbon structural steel that meets the GB/T 3078-2015 standard is preferred. The commonly used grade is 20 steel, with a carbon mass fraction of 0.17% -0.24%, a uniform metallographic structure, and good corrosion sensitivity, which can truly reflect the rust prevention ability of the medium; Avoid using steel with high alloy content, as such steel is prone to forming a passive film due to alloy elements, which can interfere with the judgment of corrosion results. In terms of specifications, the size needs to be determined according to the testing device. The conventional size is a diameter of 6-8mm and a length of 100-120mm. The surface roughness Ra needs to be controlled at 0.8-1.6 μ m. Insufficient roughness can easily lead to uneven corrosion, while excessive roughness may adsorb impurities and affect the stability of the test. The appearance selection should meet the requirements of no cracks, no scratches, no oxide scale, and rust spots. If necessary, the surface integrity should be confirmed through macroscopic observation and microscopic inspection.

Pre treatment is a key step in eliminating impurities on the surface of steel bars and unifying the surface state, which requires standardized operation according to the "cleaning drying rust protection" process. Firstly, perform degreasing cleaning using petroleum ether or anhydrous ethanol as the cleaning agent. Place the steel rod in the cleaning agent and ultrasonically clean for 10-15 minutes to remove surface oil stains, dust, and other impurities; If there is stubborn oil stains on the surface, it can be cleaned 2-3 times to ensure the removal of the oil stains and avoid the influence of the oil isolation medium on the corrosion reaction. Immediately perform drying treatment after cleaning, using hot air drying method, with a drying temperature controlled at 80-100 ℃ and a drying time of 15-20 minutes, to prevent residual moisture on the surface of the steel rod from causing natural corrosion; After drying, it needs to be cooled to room temperature to avoid contact with air at high temperatures and the formation of oxide films. Finally, the steel bars that have been dried and cooled should be tested within 2 hours. If not in use temporarily, they should be sealed and stored in a dryer for no more than 24 hours to prevent surface oxidation or contamination.

　　Liquid phase corroded steel rodIt is necessary to strictly control the selection of materials, specifications, and appearance. Pre treatment should follow standardized cleaning, drying, and storage processes to ensure the reliability of test results and provide accurate basis for evaluating the rust prevention performance of the medium.