Pickling passivation is a chemical reaction. First, the oxide scale and rust on the surface of the steel can be removed by the pickling solution, and the passivation process can be completed at the same time. It can effectively prevent the seamless steel pipe from oxidizing and achieve the purpose of anti-corrosion. The surface of the seamless steel pipe after pickling passivation becomes uniform silver white, which greatly improves the corrosion resistance of the steel pipe.
1. The effect of pickling passivation
In the process of prefabrication, welding, testing and heat treatment, iron oxide, welding slag, grease and other dirt will accumulate on the surface of seamless pipes (carbon tubes, stainless steel pipes), which will change the corrosion resistance of the pipes.
After the seamless pipe is cleaned by pickling liquid, the stolen goods on the surface of the steel pipe can be removed; after the passivation treatment, a protective film that prevents oxidation can be formed on the surface of the seamless steel pipe, thereby improving the corrosion resistance of the seamless steel pipe and ensuring safe operation of the production process.
2. The configuration of pickling solution and passivation solution
Whether the passivation solution and the passivation solution are properly formulated or not directly affects the quality of pickling passivation. Therefore, the appropriate formula should be determined according to the nature of the pipe.
When the
stainless steel pipe or equipment only needs to be pickled on a part of its area, the surface to be treated can be coated with pickling paste after removing the greasy dirt.
3. Steps and methods for pickling passivation
The pickling purification treatment can be carried out according to the following steps:
Degreasing → pickling → cold water rinse → passivation → cold water rinse → blow dry
1) Degrease
Before pickling, each pipe section should be carefully inspected. If there is grease in the pipe, it should be degreased with carbon tetrachloride (or trichloroethylene). At the same time, check the quality of the weld. If there are large welds, weld slag, etc., they should be dealt with.
2) Pickling
The pickling can be carried out by tank leaching method or system circulation method. The system circulation method is to use an acid pump to pipe acid liquid into the pipe while exhausting the air. After the air is exhausted, it is circulated until the iron embroidery is thoroughly washed. The pickling time should be increased for pipelines with serious embroidered corrosion (the specific time depends on the actual situation) until all the rust is cleaned. For special-shaped parts that cannot be dynamically pickled, static pickling is used (that is, the special-shaped parts are soaked in an acid tank until the rust is removed).
3) Neutralization
After the acid is drained, the neutralizing liquid hose on the street uses a pump to dynamically neutralize the remaining acid in the camp. Check with pH test paper at the discharge port, when the solution is neutral or weakly alkaline. That is to stop neutralization.
4) Passivation
After the pickling is qualified, connect the passivation liquid hose, start the pump to pour the passivation liquid into the tube, and exhaust the air while filling, so that the passivation liquid circulates in the closed for half an hour, and then keep it static for another two hours.
5) Blow dry
After passivation, first rinse with water, and then use dry oil-free air to completely dry the inner wall of the pipe.
As a seamless tube manufacturer, Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes: thin-wall/thick-wall seamless pipes, precision seamless pipes, small-diameter seamless pipes, providing various specifications and materials, large inventory, rich experience, and can be provided customized service according to customer requirements.
