Salt spray test method

Salt spray test method

Types of salt spray test: neutral salt spray test acetate spray test Copper accelerated acetate spray test

Function: Detecting the corrosion resistance of the coating, suitable for the quality identification of protective coatings. The box hardware is generally tested by neutral salt spray. The results can be used to compare the quality of the coating, but it cannot be used as the coating in all environments. The basis of corrosion performance.

Scope of application: Cathodic coating on the surface of metal substrate, such as nickel-chromium on copper substrate or zinc die-casting, copper-nickel-chromium, copper-nickel, copper-tin alloy-chromium coating. This method is not recommended for zinc coating. Because zinc is an anodic coating, it has self-corrosion and can protect the steel base metal. Generally, the thickness can be measured.

experiment method:

The chemically pure sodium chloride is dissolved in distilled water or ionized water at a concentration of (50 ± 5) g / L, that is, a concentration of 5%, and the pH of the solution is 6.5 - 7.2. Filter before use.

Test equipment: standard salt spray tester

Test conditions: temperature (35 ± 2) oC fog reduction: 1-2ml / h / 80cm2

Relative humidity: >95% Spray time: continuous spray

Test time: It can be determined according to the standard requirements of the covered layer or product (national standard European standard, etc.). If there is no standard, the standard can be decided by the two parties. The recommended time is 2h 6h 16h 24h 48h 96h 240h 480h 720h 960h.

Specimen: The number of samples is mainly 3 pieces, which can also be negotiated according to the cooperation between the two parties. The sample must be cleaned before the test, but the passivation film or coating layer of the plating and plating should not be damaged. The sample shall be vertically suspended in the salt spray test chamber or placed at an angle of 15-30 ° to the vertical line. The distance between the samples shall not be less than 20 mm, and the droplets on the support shall not fall onto the sample. After the test chamber has reached the test conditions, the sample is exposed to a specified time or to the specified degree of damage (the sample time should be deducted from the test sample and the spray time is interrupted). After the test, the surface of the sample is rinsed with flowing cold water. Salt spray, visual inspection and rating after drying.

Evaluation of test results: Usually the test results should be assessed by the covered layer or product standard, or by the negotiation standards of the two parties. The contents of the regular record have the following four aspects:

1. Appearance after test 2. Appearance after removal of corrosion products 3. Corrosion defects such as: pitting corrosion, cracks, distribution and number of bubbles, etc. 4. Time to start corrosion

The luggage hardware mainly requires decorative effects, followed by the minimum corrosion resistance of Zui, and the time when corrosion begins to record. The rolling materials are difficult to pass the neutral salt spray test for more than 24 hours according to the current materials and treatment methods. There is no rust, and the 608# nickel frame of the hanging electricity can pass this standard salt spray test. Anyone who has requested this test can use the hang 608# nickel frame to deal with it.

Reference materials:

Corrosion resistance test rating: (Salt spray test rating applies)

A product with a large surface area is delineated for an area of ​​5 mm 2 for calculation. The area of ​​a single test piece is smaller and the shape is more complicated. The number is determined by the number, and the transparent plexiglass or plastic with a square (5mm*5mm) is used. The film is covered on the main surface of the coating to be tested, and the main surface of the coating is divided into a number of squares, and the total number of squares is counted, set to N, (the square on the test edge, more than one-half and In the above case, the calculation of the corrosion rate is based on the calculation of a square, which is not counted, and the number of squares with corrosion points after the corrosion test is set to n.

Corrosion rate = n / N * 100%

n-----corrosion points occupy the number of grids N-----the total number of grids covering the main area

If 10 or more corrosion points are contained in any two adjacent squares, or if the area of ​​any corrosion point is greater than 2.5 mm2, the sample cannot be rated. In the rating level, level 10 zui is good, level 0 zui is poor. example:

After a salt spray test of a product, the coverage area is 164 grids (N), and the corrosion point occupies 3 grids (n). The corrosion rate is 3/164*100%=1.8%, and the corrosion assessment result is 6 grades.

Corrosion rate rating table

The above contents are taken from the "Electroplating Solution and Coating Performance Test" prepared by the Electroplating Branch of China Surface Treatment Engineering Association. For your colleagues to refer to corrections.

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