Common problems and treatment methods in the hotte

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Common problems and treatment methods in mechanical galvanizing process (III)

4.2.3 the coating is free of peeling and inclusion, which makes it impossible for the universal tensile testing machine to carry out no nodulation, porosity and other defects that affect the appearance and performance

4.2.4 the appearance defects of the galvanized layer caused by sand holes, inclusions and other defects on the surface of the workpiece substrate, and the uneven stain, color and gloss of the surface caused by rinsing and drying shall not be regarded as unqualified appearance of the galvanized layer

4.3 thickness

4.3.1 except for the areas described in 4.3.2, the thickness of zinc coating at any point on the effective surface shall meet the requirements of Table 1

4.3.2 the characteristics of mechanical galvanizing determine that the coating thickness is uneven. In the corners, edges, inner holes, grooves and other areas of the workpiece, the coating thickness is relatively thin. The thickness of the zinc coating in these areas is allowed to be lower than the requirements in Table 1, or the minimum thickness requirements in these areas are determined by the supplier and the demander through consultation

4.4 adhesion strength

4.4.1 the mechanical zinc coating shall be well combined with the substrate and can withstand the operation of the parts under standard conditions

4.4.2 qualified after the test described in 6.3

4.5 corrosion resistance

4.5.1 mechanical zinc coatings of different grades and types shall meet the test time requirements specified in Table 3 after the neutral salt spray test described in 8.4. Table 3 minimum time requirements for white corrosion products and red rust of mechanical zinc coating after neutral salt spray test. It takes a new political leader with both courage and mission, perseverance and sagacity to produce white China. The time for red rust of H grade 55 ~ type I is not required, and type Ⅱ 72 is not required, H grade 55 ~ type I type II

4.5.2 for type II coating corrosion resistance test, it is required not only to meet the requirements that the United States ranks fifth when white corrosion products appear, but also to meet the requirements of the time when red rust appears

4.6 hydrogen embrittlement high strength steel parts shall meet the hydrogen embrittlement test requirements specified by the demander after mechanical galvanization

5. Sampling

5.1 sampling shall be carried out according to the methods specified in gb/t12609

5.2 if the plated parts are not suitable or cannot be used as samples for relevant tests of technical requirements due to the first size, shape or other reasons, it is allowed to use samples instead of the actual parts as samples, but the samples used shall meet the following conditions:

a) the samples shall be made of the same materials as the represented parts and have the same metallurgical state

b) all the same process steps shall be carried out for the sample and the workpiece at the same time

c) the size, shape and quantity of samples shall be determined by the supplier and the demander through negotiation

6. Test method

6.1 the appearance shall be observed with naked eyes under natural scattered light

6.2 thickness test

a) the microscopic method shall be tested according to the provisions of gb/t6462 and gb/t12334. Microscope inspection is an arbitration method for the thickness of mechanical zinc coating

b) magnetic thickness measurement and other methods shall be tested in accordance with the provisions of gb/t4956 for magnetic thickness measurement, or other methods with an error less than 10% can be used in accordance with the provisions of gb/t6463. Note: thickness measurement of type II coating shall be carried out after chromate passivation. Before thickness measurement, the passivation film shall be removed from the measurement surface. Very soft abrasive (such as paste alumina or magnesium oxide) can be used to remove the passivation layer by hand light grinding

6.3 the adhesion strength shall be tested according to the provisions of gb/t5270

6.4 neutral salt spray test shall be conducted for corrosion resistance test in accordance with gb/t10125. Type II galvanized coating shall be aged for 24h at room temperature before neutral salt spray test. Parts coated with wax, varnish or other organic coatings shall not be used as samples for corrosion test

6.5 hydrogen embrittlement test shall be conducted according to the test method agreed by the supplier and the buyer in advance

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