Difference between CCT and NSS
The Cyclic Corrosion Test and The Neutral Salt Spray test are two different types of salt spray test methods that have significant differences in test conditions, purpose, and application.
1.CCT
Definition and purpose
The Cyclic Corrosion Test is a comprehensive salt spray test method, which simulates the complex environmental conditions of the product in practice by combining the neutral salt spray test with constant humidity and humid conditions.
This test method not only tests the corrosion resistance of the surface of the product, but also focuses on the corrosion of the product in a wet environment, so as to more comprehensively evaluate the corrosion resistance of the product.
The cyclic corrosion test is mainly used for the parts with complex structure and serious corrosion, such as automobile exhaust pipe, frame, oil pipe, etc.
Test process
The cyclic corrosion test usually involves two cycles of spray and drying for a certain period of time.
In the spray stage, convert the saline solution containing sodium chloride into salt spray and make it fall evenly on the surface of the sample.
In the drying stage, the sample is exposed to a dry environment for a period of time by controlling the temperature and humidity.
In addition, some cyclic corrosion tests will be added to the wet and heat phase to simulate worse environmental conditions.
Test standard
The criteria for cyclic corrosion tests vary among different countries and industries.
For example, the China standard GB / T 24195 (equivalent to ISO 16151) specifies the test methods for cyclic accelerated corrosion of metals and alloys under acid salt spray, dry and wetting conditions.
In addition, there are the PV 1210 standard of Volkswagen, the GMW14872 standard of General Motors and the SAE J2334 standard of the International Institute of Automotive Engineers, and these standards have formulated detailed test specifications and requirements for different types of test samples and test conditions.
2.NSS
Definition and purpose
Neutral salt spray test is one of the earliest and most widely used accelerated corrosion test methods.
It evaluates the corrosion resistance of the product by exposing the sample to a salt spray containing a neutral pH sodium chloride salt solution.
Neutral salt spray test is mainly used for the corrosion resistance test of metal and its alloy, metal coating, anodic oxide coating and other materials.
Test condition
The neutral salt spray test is usually conducted in a specific test box, where the temperature is kept at about 35℃ and the humidity is greater than 95%.
During the test, the saline solution containing (5 ± 0.5)% sodium chloride was sprayed on the sample surface in fog through the spray device, and then a certain amount of spray and spray time were maintained.
In addition, the settling speed of salt spray and the distribution of salt spray in the test box also need to meet certain requirements.
Evaluation of test results
The result evaluation of neutral salt spray test usually includes observing the appearance change of samples, measuring the corrosion area or weight change, etc.
Based on the test results, we can evaluate the corrosion resistance of the sample at different time points and predict its service life in the natural environment.
3.Sammation
The circulating and neutral salt spray tests differ significantly in terms of test conditions, purpose, and application.
The cyclic corrosion test evaluates the corrosion resistance of the product by combining various environmental conditions to simulate the complicated situation; the neutral salt spray test mainly focuses on the corrosion resistance of the sample in a single salt spray environment.
In practical application, appropriate test methods should be selected according to the product characteristics and test requirements.
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