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5 Methods for Evaluating Results of Salt Spray Corrosion Test

Posted on 09 01 ,2020 

Salt Spray Corrosion Test

The 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.

1. Express according to the characteristics of corrosives

This method is based on the appearance characteristics of the corrosion product after the salt spray test, and the corrosion characteristics of common electroplated parts after the salt spray test, such as:

Galvanized steel, gray or black plating corrosives and brown rust zinc are susceptible to chloride ion erosion, so impurities in seawater;

Iron and steel parts are chrome-plated, gray or black plated corrosives and brown rust;

Chrome plating of iron and steel parts, brown rust;

Silver-plated copper, green patina;

Copper tin plating, gray plating corrosion and green patina.

Corrosive characteristics

2. Expressed as a percentage of corrosion 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”.

A: Spots and / or color changes caused by the damage of the cover layer (different from the color of the obvious corrosion products of the base metal)

B: Difficult to see, even darkened due to invisible cover corrosion

C: corrosion products of the anodic coating

D: corrosion products of cathodic coating

E: Pitting on the surface (corrosion pits may not extend to the collective metal)

F: chipping, peeling, peeling

G: Bubbling

H: Cracking

I: Cracked

J: Chicken claw or star defect

3. Expressed in terms of corrosion rate

Standards using this method include ASTM B-117 

This method uses 5 × 5 (mm) as a small square, divides the main surface of the sample into many small squares, 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 capable of dissolving corrosive substances while not reacting with the sample itself to dissolve the corrosive substances on the sample after the test, so that the weight of the sample after the test is 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. Dividing the degree of corrosion 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.

LIB basic series and cyclic corrosion test chambers can achieve this test. Contact us to get details.

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