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Detailed explanation of pretreatment process of steel coating

Release time:

2022-09-30 15:18

Iron and steel products are often in contact with the air, due to the oxygen and water in the atmosphere and may have the role of SO2, CO2, H2S, etc., it is prone to corrosion, resulting in reduced performance or even damage of steel products. Therefore, it is necessary to eliminate the adverse factors affecting the quality of the coating in the pre-coating treatment.

The quality of steel coating pretreatment has a great influence on the quality of the coating, which is mainly reflected in the following:

1. Enhance the adhesion (binding force) of the coating to the steel surface.

2. Improve the anti-corrosion performance (anti-rust) of the coating on steel.

3. Improve the leveling and gloss of the coating.

4. Reduce coating blistering, pinholes, sand spots and other appearance defects.

 The pre-coating treatment of steel products mainly includes: degreasing and degreasing, rust removal, phosphating, silane ceramic and other processes. Process details are as follows:

 

 
01
 
 
 
 
Iron Phosphating Process

 

The characteristics of iron phosphating: iron phosphating, also known as color phosphorus, in the steel surface to form a blue-iridescent phosphating film, iron phosphating has the following advantages and disadvantages:

Advantages: simple process, easy to control, no phosphating sediment.

Disadvantages: Compared with zinc phosphating, phosphating film antirust performance is worse than zinc phosphating.

 

② Iron phosphating process flow

A, rusty steel products

Oil removal → water washing → rust removal → water washing → iron phosphating → water washing (it can also be done without water washing)

B, no rust steel products

Degreasing → water washing → iron phosphating → water washing (it can also be done without water washing)

 

 
02
 
 
 
 
Zinc phosphating process

 

① Characteristics of zinc phosphating

Zinc phosphating, also known as gray phosphorus, forms a light gray-dark gray phosphating film on the surface of steel. Zinc phosphating film has the following advantages and disadvantages:

The advantages: phosphating film uniform, compact, excellent anti rust performance. Widely used in steel coating pretreatment.

◆ Disadvantages: process control is strict with respect to iron-based phosphating, and phosphating sediment will inevitably be produced in the production process.

 

② Zinc phosphating process

A, spray zinc phosphating process

Degreasing → water washing → water washing → surface adjustment → zinc phosphating → water washing → water washing

B, immersion zinc phosphating process

Oil removal → water washing → rust removal → water washing → neutralization → water washing → surface adjustment → zinc phosphating → water washing → water washing

 

 
03
 
 
 
 
ternary phosphating process

 

① ternary phosphating, also known as electrophoretic phosphating, zinc, manganese, nickel ternary phosphating, the formation of dark gray phosphating film on the surface of steel, mainly used for steel electrophoretic coating before treatment, ternary phosphating film has the following advantages and disadvantages

◆ advantages: phosphating film uniform, compact, phosphating film acid resistance, alkali resistance, phosphating film in the process of electrophoresis without damage, to ensure the adhesion and corrosion resistance of electrophoretic coating.

Disadvantages: the need for appropriate heating, phosphating process will also produce a certain amount of phosphating sediment.

 

② Ternary phosphating process flow

A, no rust steel products ternary phosphating process

Degreasing and degreasing → water washing → water washing → surface adjustment → ternary phosphating → water washing → water washing → pure water washing → electrophoretic coating

B, rusty steel products ternary phosphating process

Degreasing → water washing → rust removal → water washing → neutralization → water washing → surface adjustment → phosphating → water washing → water washing → pure water washing → electrophoretic coating

 

 
04
 
 
 
 
Silane Pottery Process

 

① Characteristics of silane pottery

Silane ceramic process is a new environmental protection coating pretreatment process, with the following advantages and disadvantages

◆ Advantages: No phosphorus and heavy metals, almost no slag in the treatment process, and environmental protection of wastewater discharge. The performance of the coating is equivalent to that of zinc phosphating.

Disadvantages: only applicable to spray or swim immersion pretreatment line, not applicable to manual immersion line.

 

② Silane ceramic process flow

Degreasing → water washing → water washing → silane ceramic → water washing → water washing → pure water washing

Process, Phosphating, Washing, Steel, Ternary, Coating, Painting, Treatment, Products

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