In the field of materials science and engineering, corrosion testing is critical to evaluating the durability and reliability of materials. ASTM B117 is a classic corrosion test method for a wide range of applications. However, other corrosion test methods also have their own advantages, and in-depth comparison of them can provide effective reference for practitioners.
1. Test principle:
The NACL solution is atomized into salt spray by a spray device to expose the sample. The chloride ions in the salt spray will chemically react with the surface of the sample. For example, on the metal sample, the chloride ions will destroy the passivation film and trigger an electrochemical reaction, leading to metal corrosion.
2. Test equipment and conditions:
The ASTM B117 test chamber includes salt spray tank, brine storage tank, spray nozzle, etc. The temperature is usually controlled at about 35℃, the salt spray sedimentation rate is 1-2ml /80cm²·h, and the NACL solution concentration is 5%. The duration of the test ranges from a few hours to thousands of hours, depending on the characteristics of the material and the purpose of the test.
3. Scope of application:
Suitable for steel, aluminum, zinc and other metals and their coatings, coating corrosion resistance test, in the automobile, Marine, electronic equipment and other industries, used to evaluate the corrosion performance of materials in simulated Marine or salt atmosphere environment.
4. Advantages and disadvantages:
Advantages: high degree of standardization, strong comparability of different laboratory results; The equipment is simple, easy to operate and low cost, which is conducive to large-scale material screening.
Disadvantages: It is very different from the actual environment, and it is difficult to simulate the actual pollutant and humidity changes; The test period is long, and the material with good corrosion resistance will have obvious results for a long time; Focusing on macroscopic indexes such as surface corrosion morphology and weight loss, the investigation of microscopic mechanism of corrosion is insufficient.
1. Test principle:
The sample is used as the working electrode, and the reference electrode (such as saturated calomel electrode) and the auxiliary electrode (such as platinum electrode) constitute an electrochemical cell. Applying potential or current to measure the electrochemical response of the working electrode, such as the polarization curve can reflect the corrosion current density, passivation potential and other key parameters, so as to evaluate the corrosion rate and tendency.
2. Test equipment and conditions:
Need electrochemical workstations, electrolytic cells, electrode systems, etc. In specific electrolyte solutions, such as 3.5% NACL solution commonly used in research metals or other electrolytes that simulate the actual environment, the temperature and solution stirring speed can be controlled as needed.
3. Scope of application:
Widely used in the study of corrosion mechanism of metal materials, the accurate determination of corrosion rate and the evaluation of coating and coating protection performance, which plays an important role in metal research and development, surface treatment process optimization and corrosion failure analysis.
4. Advantages and disadvantages:
Advantages: The corrosion dynamic parameters can be quickly and accurately obtained, and the corrosion rate can be calculated by the corrosion current density, greatly shortening the test cycle; The microscopic electrochemical behavior, such as the formation and destruction mechanism of passivation film, can be deeply studied to provide a theoretical basis for corrosion protection. The test parameters are flexible and adjustable, and can simulate various corrosion environments and working conditions.
Disadvantages: harsh requirements on the surface state of the sample, surface treatment and electrode preparation need to be fine, otherwise affect the accuracy of the results; Due to the influence of electrolyte solution composition, temperature, instrument accuracy and other factors, the repeatability and stability of the test need to be carefully controlled. The measurement of complex samples or multiphase material systems is limited, and it is difficult to reflect the overall corrosion behavior of materials.
1. Test principle:
Place the sample in a high-temperature and high-humidity environment chamber to form a water film on the surface of the material. At high temperature and high humidity, dissolved oxygen and other impurities in water react with the material to cause corrosion, which will also accelerate the aging and degradation of the material and affect the comprehensive performance.
2. Test equipment and conditions:
The core equipment is a wet heat test chamber, which can accurately control temperature and humidity. The test temperature is generally 40-60 ℃, and the relative humidity is above 90%. The testing time can range from a few days to several months, depending on the type of material and test requirements.
3. Scope of application:
Mainly used for corrosion resistance and durability evaluation of electronic products, organic materials, coatings and some metal materials in hot and humid environment, such as electronic and electrical industry to test the reliability and stability of electronic components and circuit boards in hot and humid environment.
4. Advantages and disadvantages:
Advantages: It can better simulate the actual high temperature and high humidity environment, and it is targeted for the corrosion research of humidity sensitive materials; The equipment is easy to operate and low cost; It can observe various properties such as corrosion and aging of materials at the same time, and the comprehensive evaluation is more comprehensive.
Disadvantages: the test environment is single, and can not simulate complex factors such as salt spray and industrial waste gas; The electrochemical behavior of corrosion of metal materials is not deeply studied, focusing on macroscopic observation and measurement of material appearance and physical property changes.
1. Comparison of test principles:
ASTM B117 Reaction of salt spray chemicals with samples, salt spray environment driven; Electrochemical corrosion test active application of potential current, according to the electrochemical response assessment; The wet heat test is based on the chemical reaction and aging of water film on the surface of high temperature and high humidity materials.
2. Comparison of application scope:
ASTM B117 focuses on the simulation of corrosion resistance of metals and their coatings and coatings in atmospheric environments containing chloride ions; The electrochemical corrosion test focuses on the determination of the corrosion mechanism and rate of metal materials, which is suitable for metal materials in a variety of electrolyte environments. Wet and thermal tests evaluate the performance of moisture sensitive materials, such as electronics, organic materials and some metals, in wet and thermal environments.
3. Test cycle comparison:
ASTM B117 long cycle, especially good corrosion resistance material; Electrochemical corrosion test within hours to days to obtain key data; Moisture-heat tests range from days to months.
4. Comparison of accuracy and depth of test results:
ASTM B117 provides macro morphology and weight loss information, and the study of corrosion mechanism is shallow, reflecting the actual environment corrosion accuracy is limited; The electrochemical corrosion test can accurately measure the parameters and delve into the microscopic mechanism, but it requires high conditions and samples, and its accuracy is affected by many factors. The wet heat test focuses on the change of macroscopic properties, but the electrochemical research is insufficient, which reflects the change of the comprehensive properties of the material at high temperature and high humidity.
In short, ASTM B117, electrochemical corrosion test and wet heat test each have their own characteristics and scope of application. In practice, corrosion test methods should be reasonably selected and corrosion properties of materials should be accurately evaluated based on factors such as material type, use environment and research purpose, so as to provide a reliable basis for material development, application and quality control.
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