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Pre-treatment of Steel Enamel Product

Pre-treatment of Steel Enamel Product

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  • Time of issue:2021-10-15
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(Summary description)Generally, there are three methods for pretreatment of steel enamel, sandblasting, thermal degreasing method (air firing method) and chemical cleaning method.

Pre-treatment of Steel Enamel Product

(Summary description)Generally, there are three methods for pretreatment of steel enamel, sandblasting, thermal degreasing method (air firing method) and chemical cleaning method.

  • Categories:Company news
  • Author:
  • Origin:
  • Time of issue:2021-10-15
  • Views:0
Information

Generally, there are three methods for pretreatment of steel enamel, sandblasting, thermal degreasing method (air firing method) and chemical cleaning method.

 

Sandblasting is the most commonly used method for the pretreatment of cast iron enamel, while steel plate products are only used when the volume is larger and the thickness is more than 2mm. The surface of the body after sandblasting is clean, and the appearance is silver-white, and it can be directly coated with enamel frit.

 

The hot degreasing method is also called the empty firing method. All organic stains can be completely removed by empty firing. After empty firing, it is directly pickled without degreasing.

 

The chemical cleaning method is mainly pickling and neutralization, and it is also the most commonly used method in the production of enamel. The following introduces the standard operation of the pretreatment of the chemical degreasing method.

Degreasing → hot water washing → cold water washing → first tank pickling → flowing water washing (→ degreasing → flowing water washing → second tank pickling →) flowing water washing → nickel coating → flowing water washing → neutralization → drying

 

Degreasing:

1. The total degreasing time is 20-30 minutes

2. Degreasing temperature is 70~100℃

3. The concentration is 40~60 grams/liter (g/L) (4~6%)

4. If the surface of the utensil is still drainable, it should be degreased again.

5. The basket must move fast when it is transferred to the next processing tank.

6. Scoop off the slick oil on the degreasing fluid.

7. After saponification is selected for the use of degreasing agent, it is better that the grease can precipitate

 

Pickling:

Although hydrochloric acid can be used instead, sulfuric acid is more effective. If the concentration of hydrochloric acid is about 11%, the degreasing time at room temperature is about 20-30 minutes.

 

Generally, pickling sulfuric acid concentration is 6~8%, temperature is 65~75℃, time is 3~5 minutes. The pickling loss value is 20~50g/m^2/both sides. The pickling concentration of one enamel is 14~16%, the temperature is 70~75℃, the time is 5~10 minutes, the pickling loss is 30~50g/m^2/both sides, the pickling loss is 25 after adding nickel ~70g/m^2/both sides.

 

Nickel:

Concentration of two enamel nickel sulfate: 6~12g/L, pH: 2.5~3.6, temperature in 60~70 degrees Celsius, time 3~5 minutes. Concentration of nickel sulfate in one time: 12~15g/L, pH: 2.4~2.8, temperature at 65~75 degrees Celsius, time 5 minutes. A filter should be equipped to continuously remove iron hydroxide deposits.

 

Secondary enamel coating with nickel is not absolutely necessary, but coating with nickel can increase the adhesion of enamel and reduce the rate of defective products.

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