ShiTeng Traffic Facilities Co.,Ltd.

Quality Requirements of the Galvanized Layer Quality Requirements of the Galvanized Layer

Generally, wave-pattern guardrail, guardrail column and all parts have metal finishing through hot-dip galvanizing. In order to ensure their anticorrosion, the tests should be carried out from the adhesion amount of galvanized layer, the uniformity of the galvanized layer and the adhesion of the galvanized layer.

guardrail

1.Test of the Adhesion Amount of Galvanized Layer:
Zinc used in the dip galvanizing should be 0 zinc or 1 Zinc of GB470 rules. The adhesion amount of zinc should fit into the thickness of galvanized layer, and the test of zinc adhesion amount can adopt antimonous chloride method or layer thickness meter.
The basic principle of antimonous chloride method: Because zinc can be completely dissolved in the concentrated hydrochloric acid solution with antimonous chloride, after weighing before and after the dissolving, the zinc adhesion amount per unit area can be calculated.

2.Test of the Uniformity of Galvanized Layer:
Generally, the galvanized layer uniformity experiment adopts copper sulphate method.
Principle: Using the copper sulphate solution to etch the sample, the time and extent of the replacement of the zinc can be used to determine the uniformity of the galvanized layer.
Sample manufacture: Dissolving 36g chemical pure copper sulphate in 100ml distilled water, and then cooled it to room temperature after heating and dissolving, adding copper hydroxide or copper carbonate (1g per 21L copper sulfate solution),  after stirring and uniform mixing, leaving the solution above 24h, and the filtrate after filtration is the required sample.

Experimental methods: Taking three pieces of sample for etching test, stopping soaking for 1min each time, do not stir and move the sample. After taking out the sample, washing the sample with clean water and dry it for the next corrosion. If the zinc layer is uniform, the sample won’t turn red and be copper plated after the copper sulphate corrosion for five times. The experimental solution can only be used for etching for 15 times.

3. The Adhesion of Galvanized Layer:
The test of adhesion test of galvanized layer adopts hammering method. Placing the test piece horizontally and the hammer head should face the center of the platform. When the hammer handle is perpendicular to the base plane, let the hammer fall free, the five points are impacted parallel with the distance of 4mm. After checking the surface of the zinc layer, its adhesion can be tested according to whether or not the zinc layer is stripped and protruded. The impact point should be away from the end of the sample above 10mm and the same point can not be impacted twice.

highway guardrail

4. Data Function Experiment:
The function of steel mainly refers to mechanical functions, which can be divided into strength function, plasticity and impact toughness. Strength function indicates the steel’s resistance ability of plasticity deformation and failure, including elastic limit, submission limit, strength limit, fatigue limit and hardness. Plasticity indicates the plastic deformation ability of steel, including elongation, area reduction and cold bending. Impact toughness indicates resistance ability of steel to impact load.
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