The test standards for the magnesium chloride stress corrosion test chamber mainly revolve around the test method, sample requirements, solution preparation, test conditions, and result evaluation, aiming to simulate the stress corrosion behavior of metal materials in the magnesium chloride solution environment and evaluate their corrosion resistance. Here are some key points:
1、 Test method
Basic principle: By immersing the sample in a magnesium chloride solution and applying a certain tensile stress, simulate the stress corrosion behavior of metal materials under actual usage conditions. Evaluate the stress corrosion sensitivity of metal materials by observing the fracture time and fracture morphology of the sample.
Test types: including constant displacement method, constant load method, and slow strain rate method (SSRT), etc. Among them, the constant displacement method deforms the specimen by stretching or bending and maintains this deformation; The constant load method maintains the loading load of the specimen unchanged during the testing process; The slow strain rate rule applies a load to a specimen in a corrosive medium at a relatively slow strain rate.
2、 Sample requirements
Sample types: including flat, rod-shaped, plate-like, and rod-shaped, etc. The specific dimensions are determined according to the testing standards. For example, some standards specify that the standard dimensions for plate-shaped specimens are 2mm thick, 3mm wide, 30mm long, or 4mm thick, 5mm wide, and 30mm long; the diameter for rod-shaped specimens is 3mm or 5mm long, and 30mm long.
Sample preparation: The sample should have sufficient strength and stiffness to maintain stability during the testing process. The surface of the sample should be smooth and flawless, usually achieved through grinding and polishing to reduce the influence of surface roughness on the test results.
3、 Solution preparation
Solution composition: Prepare analytical grade magnesium chloride with distilled water or deionized water. For example, some standards stipulate that the concentration of magnesium chloride solution is about 42%, and its boiling point is heated and adjusted to 143 ℃± 1 ℃.
Solution volume: Ensure that each sample is in sufficient solution volume, such as at least 250ml per sample.
4、 Experimental conditions
Temperature: Set the test temperature according to the test requirements and usually maintain stability within a certain range. For example, some standards require the boiling point of the test solution to be maintained at 143 ℃± 1 ℃ or 155 ℃± 1 ℃.
Humidity: Under certain circumstances, it may be necessary to control humidity conditions.
Stress: Apply tensile stress to the specimen to create prestress. The application of prestress should be controlled according to the requirements of the test conditions.
Time: Set the test time to a certain value, such as 24 hours, 48 hours, etc., in order to compare and analyze the corrosion resistance of different materials.
5、 Result evaluation
Observation indicators: including macroscopic crack occurrence time (the time required from the start of the experiment to the appearance of cracks under a magnifying glass) and sample crack penetration time (the time required from the start of the experiment to the width of the crack penetrating the sample).
Evaluation method: By observing the fracture time and fracture morphology of the sample, combined with information such as fracture morphology and secondary cracks, the stress corrosion sensitivity of the metal material is comprehensively evaluated.