Salt spray test is an environmental test that mainly uses artificial simulated salt spray environmental conditions created by salt spray test equipment to assess the corrosion resistance of products or metal materials. The following mainly introduces the test methods of salt spray corrosion test.
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1. According to the Characteristics of Corrosives
This method is based on the appearance characteristics of corrosion products after salt spray test. The corrosion characteristics of common electroplated parts after salt spray test are as follows:
●Galvanized steel, gray or black plating corrosion and brown rust zinc are susceptible to chloride ion erosion, so it is unstable in seawater;
●Iron and steel parts are plated with cadmium, gray or black plating corrosion and brown rust;
●Chrome-plated steel, brown rust;
●Copper silver plating, green patina;
●Copper tin plating, gray plating corrosion and green patina.
2. Expressed as a percentage of corroded area
●This method is suitable for flat samples. If the test time is short or the sample shape is complicated, the corrosion area is difficult to determine.
●The standards used in this method are: GB / T6461-2002 "Rating of samples and test pieces after corrosion test of metals and other inorganic coatings on metal substrates" and so on.
3. Expressed in Terms of Corrosion Rate
●Standards using this method include ASTM B537 "Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure" and the like.
●This method uses 5 × 5 (mm) as a small grid, divides the main surface of the sample into many small grids, and calculates the corrosion rate of the sample.
4. Express according to weight increase or decrease
●This method is based on the change in the weight of the sample caused by the corrosion. Weighing the sample before and after the test, the weight change is divided into weight loss method and weight gain method. Both methods usually use flat samples.
●The weight loss method is an expression method that uses a chemical solvent that can dissolve corrosive substances while not reacting with the sample itself, and dissolves the corrosive substances on the sample after the test to make the weight of the sample after the test lighter than before the test. The weight loss method is expressed as the value of weight loss per unit sample area after the test.
●The weight-increasing method directly measures the increase in weight per unit sample area after the test.
5. Expression of Corrosion Degree According to Experience
●This method is based on the actual work experience to divide the corrosion degree of the sample after the salt spray test, which is a very rough expression method.
●The following statements are usually used: very severe corrosion, severe corrosion, moderate corrosion, slight corrosion, very slight corrosion, good appearance, etc.
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