Most square tubes are mostly steel tubes, which are unpacked, flattened, crimped, welded to form round tubes (maybe seamless or welded tubes), and then rolled into square tubes from round tubes and then cut into required lengths. Square tubes are divided into structural square tubes, decorative square tubes, architectural square tubes, mechanical square tubes, etc. according to their uses.

Phosphating is a whole process of organic chemistry and electrochemical corrosion to form polyphosphate conversion film, and the established polyphosphate conversion film is collectively called phosphating film. It can play a very important role in improving the anti-corrosion ability of a500 square tube. When we carry out phosphating treatment on a500 square tube, we should pay special attention to the following points:

1. Overflow water cleaning

Overflow water cleaning to ensure that the a500 square tube is fully rinsed and clean, reducing the condition of the skewer. When the overflow type needs to seep water from the bottom, a water hole overflow type is opened above the diagonal.

2. Phosphating and slag removal

The phosphating solution will produce more or less residues, and it should be indicated that it is equipped with phosphating slag removal equipment when the technology is formulated. Especially when spraying and phosphating a500 square tube, slagging equipment is indispensable. Typical slagging equipment includes: inclined column settler, upper sedimentation tower, centrifugal slagging device, paper bag sedimentation, etc.

3. Time interval

If the time interval between each step is too long, it will cause secondary corrosion of the a500 square tube during operation. Especially during pickling, after pickling and passivation, the pipe fittings are easy to oxidize, rust and turn green in the air, so it should be equipped with shrinkage water protection between processes to reduce corrosion. However, the time interval is short, and the water cannot be fully and effectively controlled, resulting in the phenomenon of stringing tanks, and even the bath liquid is destroyed. Therefore, when considering the process time interval of a500 square tube, an appropriate time interval should be selected according to the specific situation.

4. Pickling tank heating pipe

As far as possible, the selection of the material of the heating pipe of the pickling tank is not the content of the structural design. If no reminder is given, it may lead to the carelessness of the staff during the design of the mechanical equipment. For hydrochloric acid and sulfuric acid pickling and passivation, the pickling tank materials can only use FRP anticorrosion, granite, and plastic, and the heating tube can only use lead-antimony alloy tubes and ceramic tubes, and stainless steel plates cannot be used. If ammonium sulfate pickling passivation is used, the pickling tank and heating pipe raw materials can be stainless steel plates, natural glass fiber reinforced plastics, plastics, granite, etc.

5. Process hole

For the a500 square tube, which is prone to blind water storage, it is necessary to select a suitable place to drill the process hole to ensure that the water can be fully drained in a short period of time. Otherwise, it will cause stringing grooves or long-term drying at high altitudes, causing secondary corrosion and affecting the phosphating effect.