Pickling and phosphating is a very important step in storage rack pretreatment, which has a great influence on rack quality and service life.
Acid pickling and phosphating is a very complicated and laborious process. The preliminary treatment of some large factories is pickling and Phosphating for a whole day. At present, because of the cost and environmental protection, many factories no longer carry out acid pickling and phosphating.
The first step of pickling and phosphating is degreasing. Degreasing is degreasing with a high-temperature alkali solution, which is to remove the grease on the surface of the processed steel workpiece. This step is actually divided into even small steps, one is pre degreasing, and the other is the main degreasing. After each degreasing, water washing is required.
The second step is to remove rust. To remove rust, acid (hydrochloric acid) is used to soak. In other words, acid is used to remove the rust on the surface of the steel workpiece. Generally, a new steel plate can be processed once. If it is produced and placed for a period of time, there will be a lot of rust, which requires multiple derusting. After rust removal, wash with water.
The third step is a surface adjustment, also known as surface adjustment. It is to neutralize the processed parts with weak alkali or acid because acid and alkali on the surface of steel workpiece are harmful to spraying. Therefore, the acid and alkali should be neutralized to neutralize the acid and alkali on the surface of the steel workpiece (measuring the pH value). Sometimes this process can not be handled at one time. After the surface adjustment is completed, wash it with water.
The fourth step is phosphating, phosphating is also known as zinc phosphating, the purpose is to appear a layer of phosphating film on the surface of steel workpiece, this film is very fine, with this layer of film, it can prevent steel and air contact, prevent its oxidation and rust, also can better adhere to the plastic powder in the later spray production line.
The fifth step is passivation. Passivation is the last technical operation of acid pickling and phosphating. The purpose is to remove a large amount of powder attached to the surface of phosphating film after phosphating. These powders have an impact on the spray paint, and then wash them with water.
The sixth step is drying, which is the last step of acid pickling and phosphating. After processing, the steel workpieces after water washing are dried with a dryer to remove the moisture on the surface of steel workpieces.
The processing time of each step above is 40 minutes, including washing, so if you calculate all the steps, you may not be able to complete them in one day. In the process of surface treatment, the investment of various chemicals is very huge, and the greater investment is the investment of environmental protection treatment.
Therefore, many manufacturers now say that they are acid pickling and phosphating, but the price is very low. There must be something wrong with it. It is not false propaganda that there is no pickling and phosphating at all, or the products are shoddy. It is generally believed that the cost of acid pickling and phosphating is about 1 yuan per kilogram (liquid medicine cost, site cost, labor cost, environmental protection cost, etc.).
The difference between pickling and phosphating is that the storage racks without pre-treatment may be the same as the ones that have been treated before leaving the factory, but there is no grease removal, rust removal, phosphating, etc. These things still exist on the surface of the steel workpiece, and the surface looks very good (in fact, the surface can be distinguished, the surface without pretreatment is uneven, many small bubbles, small spots, etc.), it can be used for a period of time, and if the environment is relatively humid, the paint surface that can be sprayed for half a year will begin to crack and rust and the warehouse rack will be completely rusted after more than a year. Even if the environment is relatively dry, the service life of the storage rack is less than half that of the rack that has been pretreated.
Post time: Aug-17-2020