Salt spray test standards and determination of test results

Standards are uniform provisions for repetitive things and outlines. The salt spray test standard is a clear and specific stipulation for the salt spray test conditions, such as temperature, humidity, sodium chloride solution concentration and pH value, etc., and also puts forward technical requirements for the performance of the salt spray test chamber. The salt spray test standard for the same product should be selected according to the characteristics of the salt spray test, the corrosion rate of the metal, and the sensitivity to salt spray. The following introduces several salt spray test standards, such as GB/T2423.171993 'Basic Environmental Test Procedure Test Ka for Electrical and Electronic Products: Salt Spray Test Method：Salt spray, alternating (sodium chloride solution)”, GB593886 “Test Method for Corrosion Resistance of Metallic Coatings and Chemical Treatment Layers of Light Industrial Products”, GB/T177191 “Determination of Neutral Salt Spray Resistance of Paints and Varnishes”. (Guide: Technical Article of Material Testing Machine)

The purpose of the salt spray test is to assess the salt spray corrosion resistance of the product or metal material, and the result of the salt spray test is the judgment of the product quality. Whether the judgment result is correct and reasonable is to correctly measure the product or metal The key to the quality of salt spray corrosion resistance. The methods for judging the results of the salt spray test include: rating judging method, weighing judging method, corrosive appearance judging method, and corrosion data statistical analysis method. The grading method is to divide the percentage of the corrosion area to the total area into several grades according to a certain method, and use a certain grade as the basis for qualified judgment, which is suitable for evaluation of flat samples;

The weighing method is a method of weighing the weight of the sample before and after the corrosion test, and calculating the weight of the corrosion loss to evaluate the corrosion resistance of the sample. It is especially suitable for the corrosion resistance of a certain metal. Assessment

The method of determining the appearance of corrosive substances is a qualitative method. It determines whether the product has corrosion after salt spray corrosion test to determine whether the sample is corroded. This method is mostly used in general product standards;

Corrosion data statistical analysis method provides methods for designing corrosion tests, analyzing corrosion data, and determining the confidence level of corrosion data. It is mainly used to analyze and count the corrosion situation, rather than specifically to determine the quality of a specific product.

There are three types of salt spray test: neutral salt spray test (NSS), acetic acid salt spray (AA SS) and copper accelerated acetic acid salt spray (CA SS, also known as copper chloride acetic acid salt spray). The most widely used is the neutral salt spray test. The basic content of the salt spray test is to spray 5% sodium chloride aqueous solution in the test chamber at 35 degrees Celsius to simulate the accelerated corrosion method of the seawater environment. The length of its resistance time determines the corrosion resistance. The volume of the salt spray tank is not less than 012m 3. It is best not to be less than 014 m3, the temperature inside the tank is 35℃± 2℃, the spray pressure is 70～170kPa, at least two salt spray collectors, and the collection area is 80 cm2 each. The direction is 15～30° to allow the salt spray to settle freely on the surface to be tested. It cannot be sprayed directly. The test support is made of glass or plastic. The test pieces cannot touch each other or drip; the temperature in the box is 35℃±2℃, each The collector collects 1~2ml of solution per hour on average (the average is taken over 16 hours).

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