Hydrochloric acid is often used to remove rust on the surface of steel. Due to the emphasis on production and the pursuit of output, the pickling solution has always been at a higher concentration, but the control and maintenance of the optimal concentration of the pickling solution are ignored. Many manufacturers simply adopt Renew the acid solution once a week, or do not replace the acid solution for a long time, but often pour out some new acid solution and add some new acid solution, which causes excessive consumption of hydrochloric acid, increases production costs, and causes certain environmental problems Pollution.

Research has shown that the speed of pickling not only depends on the concentration of the pickling solution, but also depends on the saturation of Fecl2 at the concentration of hydrochloric acid. When the concentration of hydrochloric acid reaches 10%, the saturation of Fecl2 is 48%; when the concentration reaches 31%, the saturation of Fecl2 is only 5.5%, and the saturation of Fecl2 increases with temperature.

To make the steel surface after pickling the best clean surface in the shortest time, the key lies in choosing the concentration of hydrochloric acid, the content of Fecl2, and the solubility under the concentration of hydrochloric acid. Therefore, to increase the pickling speed, it is necessary to have a proper hydrochloric acid concentration and a certain Fecl2 content, but also a higher amount of Fecl2 dissolution. Among these three parameters, the concentration of hydrochloric acid is the most important. Lowering the concentration of hydrochloric acid can not only accommodate more The content of Fecl2 is not easy to be saturated, which can better solve the pickling quality of steel products.

Practice has proved that the control of the concentration range of hydrochloric acid is too narrow and too wide, which brings certain difficulties to operation and production. According to the actual continuous production and the influence of many man-made factors, we believe that the recommended concentration of hydrochloric acid should be controlled at 8~13%, the temperature of the acid solution should be between 20～40℃, and the specific gravity of the acid solution should be 1.35～1.20, which can better meet the production requirements. Need to maximize the service life of the acid. If the Fecl2 content is high, the hydrochloric acid concentration can be set to a low value; if the Fecl2 content is low, the hydrochloric acid concentration can be set to a high value.

In specific operations, it is necessary to frequently prevent the decrease of acid concentration and the decrease of acid level, and it is necessary to add new acid. When adding acid, it is necessary to do one diligence and two less, that is, add acid frequently and add less acid each time. If the pickling speed in winter is slow, it can be heated to 20-25°C, the FeCl2 content is too high, and the specific gravity of the acid solution exceeds 1.35, it can be diluted with water and finally the specific gravity of the acid solution is not more than 1.22.

In order to solve the problem of a large amount of acid mist emitted from the hydrochloric acid pickling tank during storage and work, causing environmental acid mist pollution and iron matrix dissolution during pickling of steel, resulting in over corrosion and hydrogen embrittlement, high-efficiency acid mist suppression can be used A high-efficiency rust removal solution at room temperature is prepared by the agent, corrosion inhibitor and hydrochloric acid solution, which removes the oxide scale at room temperature, has a fast rust removal speed, does not produce over-corrosion, and improves the surface and internal quality of the workpiece. There is almost no hydrochloric acid near the acid tank. It has a pungent smell and the rust removal rate is not less than 98%. Continuous addition and use can extend the service life of the rust removal liquid and equipment, and save fuel and energy consumption. The preparation and process conditions of the pickling solution are as follows: (weight percentage) hydrochloric acid (33%) 55, rust removal additive 10, water 35, temperature 20-40°C. The rust removal additive is composed of organic acid, sodium alkyl sulfate, hexamethylenetetramine, polyethylene glycol, phosphoric acid and water.