Metal surface treatment method

Metal surfaces are inevitably oxidized during various heat treatment, machining, transportation, and storage processes to produce a thick and uneven oxide layer. At the same time, it is also susceptible to various oil pollution and adsorption of some other impurities.

For oil stains and certain adsorbents, the thinner oxide layer can be washed with solvent, chemically and mechanically, or directly with chemical treatment. For heavily oxidized metal surfaces, the oxide layer is thicker and cannot be directly cleaned with solvents and chemically treated, but is preferably mechanically treated first.

The treated metal surface is generally highly reactive and is more susceptible to contamination by dust, moisture, and the like. For this purpose, the treated metal surface should be glued as quickly as possible.

The metal storage period after different treatments is as follows:

(1) wet blasting aluminum alloy, 72h;

(2) chromic acid-sulfuric acid treated aluminum alloy, 6h;

(3) anodized aluminum alloy, 30 days;

(4) sulfuric acid treated stainless steel, 20 days;

(5) blasted steel, 4h;

(6) Brass treated by wet blasting, 8h.

1. Aluminum and aluminum alloy surface treatment methods

[method 1]

Degreasing treatment. Wipe with a damp cotton dampening solvent to remove the oil, then wipe it with a clean cotton cloth several times. Commonly used solvents are: trichloroethylene, ethyl acetate, acetone, methyl ethyl ketone and gasoline.

[Method 2]

After degreasing, chemically treat in the following solutions:
Concentrated sulfuric acid 27.3 potassium dichromate 7.5 water 65.2
After immersion at 60-65 ° C for 10-30 min, remove it with water, dry it or dry it below 80 ° C; or wash it in the following solution and then dry it:
Phosphoric acid 10 n-butanol 3 water 20
This method is suitable for phenolic-nylon glue and the like, and the effect is good.

[Method 3]

After degreasing, chemically treat in the following solutions:
Ammonium hydrogen fluoride 3-3.5 Chromium oxide 20-26 Sodium phosphate 2-2.5 Concentrated sulfuric acid 50-60 Boric acid 0.4-0.6 Water 1000
It is immersed at 25-40 ° C for 4.5-6 min, that is, washed with water and dried. The method has high bonding strength and is glued within 4 hours after treatment, and is suitable for epoxy glue and epoxy-butyronitrile glue.

[Method 4]

After degreasing, chemically treat in the following solutions:
Phosphoric acid 7.5 chromium oxide 7.5 alcohol 5.0 formaldehyde (36-38%) 80
Immerse at 15-30 ° C for 10-15 min, then wash with water at 60-80 ° C and dry.

[Method 5]

After degreasing, anodizing in the following solution:

Concentrated sulfuric acid 22g/l
The mixture was immersed for 10-15 min under a direct current intensity of 1-1.5 A/dm 2 , and further immersed in a saturated potassium dichromate solution at 95-100 ° C for 5-20 min, then washed with water and dried.
Metal surfaces are inevitably oxidized during various heat treatment, machining, transportation, and storage processes to produce a thick and uneven oxide layer. At the same time, it is also susceptible to various oil pollution and adsorption of some other impurities.

For oil stains and certain adsorbents, the thinner oxide layer can be washed with solvent, chemically and mechanically, or directly with chemical treatment. For heavily oxidized metal surfaces, the oxide layer is thicker and cannot be directly cleaned with solvents and chemically treated, but is preferably mechanically treated first.

The treated metal surface is generally highly reactive and is more susceptible to contamination by dust, moisture, and the like. For this purpose, the treated metal surface should be glued as quickly as possible.

The metal storage period after different treatments is as follows:

(1) wet blasting aluminum alloy, 72h;

(2) chromic acid-sulfuric acid treated aluminum alloy, 6h;

(3) anodized aluminum alloy, 30 days;

(4) sulfuric acid treated stainless steel, 20 days;

(5) blasted steel, 4h;

(6) Brass treated by wet blasting, 8h.

1. Aluminum and aluminum alloy surface treatment methods

[method 1]

Degreasing treatment. Wipe with a damp cotton dampening solvent to remove the oil, then wipe it with a clean cotton cloth several times. Commonly used solvents are: trichloroethylene, ethyl acetate, acetone, methyl ethyl ketone and gasoline.

[Method 2]

After degreasing, chemically treat in the following solutions:
Concentrated sulfuric acid 27.3 potassium dichromate 7.5 water 65.2
After immersion at 60-65 ° C for 10-30 min, remove it with water, dry it or dry it below 80 ° C; or wash it in the following solution and then dry it:
Phosphoric acid 10 n-butanol 3 water 20
This method is suitable for phenolic-nylon glue and the like, and the effect is good.

[Method 3]

After degreasing, chemically treat in the following solutions:
Ammonium hydrogen fluoride 3-3.5 Chromium oxide 20-26 Sodium phosphate 2-2.5 Concentrated sulfuric acid 50-60 Boric acid 0.4-0.6 Water 1000
It is immersed at 25-40 ° C for 4.5-6 min, that is, washed with water and dried. The method has high bonding strength and is glued within 4 hours after treatment, and is suitable for epoxy glue and epoxy-butyronitrile glue.

[Method 4]

After degreasing, chemically treat in the following solutions:
Phosphoric acid 7.5 chromium oxide 7.5 alcohol 5.0 formaldehyde (36-38%) 80
Immerse at 15-30 ° C for 10-15 min, then wash with water at 60-80 ° C and dry.

[Method 5]

After degreasing, anodizing in the following solution:

Concentrated sulfuric acid 22g/l
The mixture was immersed for 10-15 min under a direct current intensity of 1-1.5 A/dm 2 , and further immersed in a saturated potassium dichromate solution at 95-100 ° C for 5-20 min, then washed with water and dried.

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