Neutral Salt Spray Test (NSS): 5% sodium chloride solution is used, pH 6.5~7.2, temperature 35℃, sedimentation rate 1~2ml/(h-80cm²), applicable to routine testing.
Author: Anna
I. Test Methods and Conditions
Test type
Neutral Salt Spray Test (NSS): 5% sodium chloride solution is used, pH 6.5~7.2, temperature 35℃, sedimentation rate 1~2ml/(h-80cm²), applicable to routine testing.
Acetate spray test (ASS): add glacial acetic acid on the basis of NSS, pH reduced to 3, corrosion rate accelerated by 3 times.
Copper Salt Accelerated Acetate Spray Test (CASS): further strengthen the acidic environment, used for high-precision or severe scenario testing.
Test Parameters
Salt solution concentration: 5% sodium chloride solution is the main, the purity needs to meet the standard to avoid impurity interference.
Temperature: Normally set at 35±2°C to ensure environmental stability.
Spray rate: control the sedimentation rate to ensure uniform coverage of the specimen surface.
II. Evaluation Process and Criteria
Sample handling
Samples should be placed according to the standard, to ensure that the salt spray evenly covers the surface, to avoid blocking or piling up.
Observation of corrosion phenomenon
Appearance inspection: Observe whether rust spots, blistering, flaking and other defects appear after the test.
No trace of corrosion (rating 10) indicates excellent corrosion resistance; substrate corrosion (rating ≤ 2) is judged to be unqualified.
Quantitative analysis
Measurement of quality change: compare the quality loss of the specimen before and after the test, the smaller the loss, the stronger the corrosion resistance.
Analysis of corrosion products: Detect the composition of surface corrosion products (e.g. zinc oxide, zinc chloride) and judge the degree of corrosion.
III. Standard Compliance
International standard: ISO 1461 (coating thickness and corrosion resistance), ASTM B633 (zinc plating specification).
Industry requirements: Automotive parts are usually required to pass more than 500 hours of testing, while consumer electronics products are adjusted according to actual needs.
IV. Notes
Interpretation of results: A small amount of white rust (zinc oxidation products) is permitted, but substrate corrosion is judged to be a direct failure.
Environmental control: avoid high temperature and high humidity after passivation to prevent secondary oxidation from affecting the accuracy of the rating.
Through the above steps, the corrosion resistance of the electroplated zinc layer can be systematically assessed, and provide data support for process improvement.