What is the oil content of the compressed gas in the salt spray test?

In the salt spray test, the oil content of the compressed gas should be strictly controlled within 0.01 mg/m & sup3; this standard is based on the ISO 8573-1 compressed air quality level, the specific analysis is as follows:

the Core Basis of 1. Oil Content Control

1. international Standard (ISO 8573-1)
   the standard divides the compressed air quality into several grades, of which the highest grade (Class 0) requires oil content ≤ 0.01 mg/m & sup3;. As a test to simulate extreme corrosive environment, salt spray test needs to use ultra-pure compressed air to avoid oil interference test results.

2. Domestic standard (GB/T 10125)
   although GB/T 10125 does not directly specify the oil content, it clearly requires that the compressed air should be treated with "degreasing, drying and preheating. Combined with ISO standard, it can be inferred that the oil content of compressed air for salt spray test should reach Class 0 or Class 1(≤ 0.1 mg/m & sup3;) level.

3. Industry Practice
   high-precision industries such as medicine and electronics have generally adopted the ISO 8573 Class 0 standard to ensure that compressed air will not introduce impurities to affect product performance. Salt spray test as a key means of material corrosion resistance evaluation, also need to follow this requirement.

Influence of 2. oil content exceeding standard

1. interference test results
   the oil may form a protective film on the surface of the sample, delaying the corrosion process and causing the test results to deviate from the true value. For example, the oil film may extend the corrosion time of the metal specimen several times, and it is impossible to accurately evaluate its salt spray resistance.

2. Contamination test equipment
   the accumulation of oil in the salt spray test chamber will block the nozzle, corrode the pipeline, and affect the spray uniformity and equipment life. For example, grease may cause the nozzle hole diameter to become smaller, causing the salt spray settlement to deviate from the standard value (1.0 to 2.0mL/(h · 80cm²)).

3. Violation of standard requirements
   if the oil content of the compressed air used in the test exceeds the standard, the test results may be judged invalid, and the test needs to be re-tested, increasing time and cost.

3. oil content detection and control method

1. detection method
   • compressed air quality detector: Absorb the oil mist in the compressed air through the oil detection box, and compare it with the standard view to determine the oil content after 5 minutes.
   • infrared spectrophotometry: Extract the oil in the compressed air with tetrachloroethylene, and calculate the oil content through infrared spectrum analysis, the measurement range can reach 0.01 mg/m & sup3;.
   • laser particle counting method using laser light scattering technology to detect the number of salt particles and oil droplets in salt spray, real-time monitoring of oil content changes.
2. Control measures
   • installing air cleaner multi-stage filter device is connected in series in the compressed air pipeline to remove impurities such as oil mist and dust.
   • Regular maintenance of equipment: Disassemble the cleaning nozzle every 500 hours and check the filter element of the air cleaner to ensure its filtration efficiency.
   • Use oil-free compressor: Prevent oil from entering the compressed air system from the source, reducing subsequent processing costs.