From the searing sun on hot summer afternoons to driving snow on cold winter nights, extreme weather will be your materials' playground, making them highly susceptible to corrosion. You need a testing procedure that puts your metals under the harshest of treatments to assess their resilience. A salt spray test is the ideal solution. Among the most tried and true corrosion resistance assessments on the market is salt spray testing – or salt fog testing, as it's also known. Salt spray testing is leveraged in a variety of industries and can provide you with the intelligence you need to determine just how vulnerable your materials are to corrosion and what you need to do to make it more impervious to the effects of moisture, heat, cold and other environmental impacts.
If you're unfamiliar with how a salt spray test works and what salt spray testing involves beyond the obvious (i.e., salt), this article can provide you with more insight into what it is and why it's important to have done.
What is a salt spray test?
Salt spray testing is an accelerated means of figuring out the degree to which metals, ceramic surface coatings, stainless steel and other materials have the potential to corrode in an abrasive environment. With the test carried out in a laboratory – typically within the confines of a temperature-controlled salt spray chamber -a salt spray test expedites the corrosion process by saturating the test specimen for a given time period with the blend of ingredients known to cause corrosion. Generally speaking, the longer that the test specimen is exposed to the caustic environment, the more susceptible it is to corrosion and how this natural process manifests itself.
Because the entirety of the corrosion testing process is scientific and standardized, it can provide you with accurate, actionable insight into what solutions are necessary to increase the corrosion resistance of materials before deploying them in real-world applications.
How is a salt spray test conducted?
In addition to the test specimen in question, a salt spray test or salt fog test requires the proper equipment and solutions. Depending on the specific type of test being conducted (e.g., ASTM B117, ASTM G85, ASTM D1654, etc.), they generally include all of the following:
- Salt water
- Spray nozzle
- Salt spray test chamber
The salt water isn't just any salt water, but acetic acid. Also known as ethanoic acid, acetic acid salt spray is similar to vinegar and contains 5% sodium chloride by volume. With an air pressurized spray nozzle, the test specimen is coated in a fine mist or salt fog. Within the salt spray chamber, the salt fog saturates whatever is being tested so the entirety of the material receives equal treatment. The precise amount of salt spray used – and for how long – is influenced by the type of test being conducted and the material subjected to salt spray testing. For example, for steel materials – including stainless steel – a neutral salt spray test is the most common. Neutral salt spray has a pH level of between 6.5 and 7.2. In terms of time, for materials like painted components, the testing is done over a four-day period, which is the equivalent of 96 hours.
What is ASTM B117?
Perhaps the most widely deployed of the salt spray testing methods, ASTM B117 is a standardized test that is used for metals, whether coated or uncoated. ASTM B117 helps to define the conditions that the test must mirror to assess a metal's corrosion resistance. Those conditions are defined by ASTM International or the American Society for Testing and Materials. In the case of ASTM B117, the salt spray must have a pH of 6.5 to 7.2, contain 5% sodium chloride by volume and the salt spray chamber temperature must maintain a constant air temperature of 95 degrees Fahrenheit (35 C). While there's no predetermined length that an ASTM B117 test runs for, they're usually carried out over a minimum of 96 hours (4 days) to a maximum of 600 hours (25 days).
What are the benefits of salt spray testing?
The salt spray test is used as often as it is for many reasons, but chief among them is the insight that can be gleaned from the results. It gives you an idea of the level of corrosion resistance a material has before it's put to use. But there are several other advantages as well.
Speed: Salt spray tests essentially accelerate the corrosion process so you can apply the time period in a testing environment to a real-world environment.
Affordable: Whether you're a small business owner or own a large multinational corporation, salt spray tests are easy to do and cost less than you might expect.
Accurate: Because it's standardized and conducted in a laboratory setting, the testing services mimic the effects of corrosion in their true-to-life circumstances.
Whether you're looking for a salt spray test, environmental test chamber or insight into what treatments work best for corrosion resistance, Auto Technology has the resources and every test method that you need. Contact us today to learn more.