How to use Salt Spray Testing for corrosion resistance

What Does Salt Spray Testing Mean?
An accelerated corrosion test called the salt spray test is used to compare the corrosion resistance of materials that have been exposed to salt spray or salt fog at high temperatures. This corrosion test aims to reveal information about the corrosion resistance of metals and coated metals. Following this test, it is possible to assess whether coatings, paints, and metals are suitable for exposure to maritime environments or corrosion resistance. The fog test and ASTM B117 are other names for the salt spray test.

Salt Spray Testing
The ASTM B117-compliant salt spray test involves placing samples in an enclosed salt spray testing cabinet or chamber and exposing them to continuous indirect fog or spray of a salt water solution. The test is conducted in this environment the entire time.
To gauge typical corrosion resistance in settings similar to those found in ocean water, the ASTM B117 Salt Spray Test standard is frequently employed. The length of the test relies on the specification or the material’s ability to resist corrosion.

The salt spray test can be used to compare the corrosion resistance of different metals or finishes; measure the corrosive inclination when a metal or coated surface is scratched; assess coating adhesion and corrosion creep; and assess corrosion resistance in a marine environment.

Because it is reasonably repeatable and well-standardized, salt spray testing is common. Salt spray tests are widely used in business, marine, automobile and aircraft and military hardware industry to assess how well components or completed surfaces resist corrosion.

Testing Process
The ASTM B117 testing protocols are commonly followed while performing the salt spray testing standard. The ASTM B117 salt spray test describes the best practices for conducting a salt corrosion test, including how to set up and maintain the test environment to ensure consistent findings from one testing lab to the next. In order to simulate extremely corrosive conditions, specimens are put in a closed chamber and subjected to a dense metal fog.

The tests use a 5 percent sodium chloride solution with a pH between 6.5 and 7.2 and can last anywhere from 8 to 3,000 hours (more or less in certain situations). The specimen is inspected to assess corrosion after having been exposed to the corrosive environment for the predetermined amount of time (the appearance of rust or other oxides). To be approved, the specimen must be devoid of all corrosion indications.

Instrumentation
The calibration of all measuring devices is required. A test date and the date of the calibration renewal should not fall on the same day. At the very least, the corrosion enclosure should be calibrated for the chamber’s air temperature. A relative humidity sensor can be installed in corrosion chambers. Since it is not used during salt corrosion testing, calibration is not required.

Before usage, all equipment should also be calibrated. This includes the portable pH meter that is calibrated in accordance with the manufacturer’s instructions and using certified buffer solutions. The first solution has a pH of 4, whereas the second one has a pH of 7. +/- 0.01 is the allowed tolerance. When finished, an electrode rinsing solution is used to rinse the electrode. A standard liquid refractometer solution is used to calibrate the salinity refractometer.

With automatic temperature compensation, a salinity refractometer may provide a direct reading of the percentage of sodium chloride in the range of 0 to 28 percent. A conductivity meter, which is used to measure the conductivity of water and saline solutions and is calibrated using standard solutions.

If necessary, the temperature of the chamber can be continually recorded using a data logger that has been independently calibrated, or, depending on the model, the chamber may have an Ethernet output for viewing and recording this curve. It might be sufficient to manually read the chamber temperature each day using the chamber display on a tracking sheet for salt spray testing.

Saline is exposed via atomization with compressed air. “Heated and humidified” air should be given to the spray nozzle. The temperature of the air saturator in the chamber is changed in accordance with the pressure at the atomizer pressure gauge by forcing air through it.

Pros and Cons of a Salt Spray Test
Because it is effective, affordable, well standardized, and reproducible, salt spray testing is widely used. Despite some debate over the relationship between the length of a salt spray test and the anticipated lifespan of a material, this test has become very popular because of its prompt results.

It takes far too long to test corrosion resistance in a real-world setting. Testing has little use in forecasting how materials or surface coatings would withstand corrosion in the actual world since it cannot accurately simulate exact real-world corrosive conditions. Today, the majority of salt spray chambers are employed to keep coating operations to a standard rather than to anticipate the corrosion resistance of a coating. Multiple industries, including the military, healthcare, aerospace, and many more, have numerous uses.

Conclusion
Although salt spray testing is not a perfect replica of the extremely complex natural corrosion process, it is a reliable approach to assess corrosion resistance and is frequently used as the benchmark for coating procedures. We advise using one of our PA-10 actuators with the salt spray option for applications that call for corrosion resistance.

FAQs
What are the most popular salt spray test testing criteria?
SAE J2334, ISO 9227, EN 1670, JIS Z 2371, DIN 50021, ASTM B 117, NEMA 250, UL 50E, ASTM G 85, ASTM B 368, and other standards.

What do NSS, CASS, and AASS mean?
The abbreviations “Neutral Salt Spray Test,” “Copper Accelerated Acetic Acid Salt Spray Test,” and “Acetic Acid Salt Spray Test” all stand for the same thing. They employ various salt solutions and have varying PH values.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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