How can an accelerated Salt Spray Test be used

Salt spray testing

Salt spray testing simulates a corrosive salty environment in the laboratory. It is used to speed the testing of surface coatings’ capacity to withstand air corrosion. It is one of the oldest testing procedures used in the HVAC-R coatings business and, as such, is frequently referred to when selecting HVAC-R coatings.

The utility

The salt spray test establishes

• Corrosion resistance of certain metals or coatings
• When a metal or coated surface is scratched, the corrosive inclination is measured.
• Determine the adherence of the coating and the corrosion creep
• In a marine environment, assess corrosion resistance (wetness, temperature, salt fog)

Areas of use

Because it is well standardized and reasonably repeatable, salt spray testing is common. Salt spray tests are widely used in the following industries to assess the corrosion resistance of parts or finished surfaces:

• Industry
• Marine
• Automotive
• Aircraft and military equipment

Where is salt spray test used?

We employ salt spray testing in two methods when developing and evaluating HVAC-R and radiator coatings. Salt spray testing is utilized as a stand-alone corrosion resistance test as well as an ISO 12944-9 component (previously known as ISO 20340). The salt spray method is handled the same way for both tests, in accordance with ASTM B-117.

The procedure

To begin, tiny panels (usually 35 or 46 inches in length) are created with the coating to be evaluated. The edges and backs of the panels are often protected with tape. The panel is then “scribed” with a sharp tool to create a scratch through the coating to the metal substrate.

The prepared panel is then placed inside the test cabinet. Racks in the cabinet keep the panels in place as defined by ASTM B-117, angled back 15 to 30 degrees from vertical. The cabinet is then closed, and a 5 percent salt solution is supplied into it at a steady pace and temperature using an atomizer. Salt fog is blasted upwards, causing droplets to fall and settle on the panels.

Following this, the test panels will be checked on a regular basis, and the salt spray cabinet will be monitored to verify that it performs properly during the test. During these brief panel evaluations, it is established whether the test is continuing as planned or if the coating on the test panels is prematurely degrading.

The fundamentals of the test are as stated above, notwithstanding the fact that each laboratory has a slightly different setup. A salt spray tester is distinguished by having a cabinet with a digital readout that shows the total number of hours the test cabinet has been in operation as well as alarms that sound when certain crucial events occur, including when the level of the salt solution drops. These characteristics are crucial because some salt spray tests last for incredibly lengthy periods of time. For instance, some testers have undergone more than 6,000 hours of testing to ASTM B-117. That is a little more than 8 months’ worth of nonstop salt spray in a row.

The corrosion protection is measured using both ASTM B-117 and ISO 12944-9, although there are several key differences between the two tests. Unlike B-117, which only tests for static salt spray, ISO 12944-9 tests for a total of 168 hours over the course of one week, including 72 hours of UV exposure, 72 hours of salt exposure, and 24 hours of freezing. The UV, salt spray, and freeze cycles are repeated 25 times for a total of 4,200 hours. ISO 12944-9 is far more like the extreme weather cycles that HVAC-R devices are frequently exposed to in the real world, even though neither test is conducted in an actual outside environment.

The flipside

The article Studies show that the ASTM-B117 salt spray test does not correlate with real-world scenarios discusses the differences between these two tests and why ISO 12944-9 testing is so important. According to the Society for Protective Coatings (SSPC), “combined corrosion / weathering is a substantial improvement to the traditional salt spray test (ASTM B117) in terms of reproducing atmospheric corrosion in an accelerated fashion.”

Corrosion Test Method

The fasteners might have been mounted on a military vehicle to carry out numerous battlefield operations or a comprehensive durability test. Instead, accelerated life test sequences that would imitate these conditions were created, based on military protocols described in Def Stan 00-35 and Mil Stan 810F. This comprised salt spray corrosion chamber tests and corrosion tests according to ASTM B117. While minimizing the lead time and expenses for the customer, this accelerated life testing revealed whether the fasteners would meet military specifications.

FAQs

How is a salt spray test performed?

Tests for salt spray are carried out in an enclosed testing chamber. A brine is applied to a sample using a spray nozzle. The goal of this dense saltwater fog is to mimic a corrosive experiment. The evaluation of oxide appearance is based on how long corrosion takes and how corrosion-resistant a product is.

What is accelerated corrosion test?

Since the early 1900’s, accelerated corrosion testing has been performed to evaluate the effectiveness of coatings when exposure to actual circumstances is neither possible nor available. An accelerated corrosion test is often defined as any test procedure that yields results in a shorter amount of time.

How do you accelerate corrosion?

Corrosion rate can be increased by raising the temperature of the cell, stirring the solution, increasing the percentage of NaCl in the solution, and increasing the current rate. The induced current approach and the artificial climate environment are the two major tests for accelerating corrosion in RC.

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