Accelerated Corrosion Testing Methodology
In an accelerated corrosion test, materials and products undergo corrosion, deterioration, or failure in a shorter amount of time than under normal conditions while maintaining the same corrosion mechanism(s). The ASTM B117, popularly known as the salt spray test, is the most popular accelerated corrosion test.
To determine whether a coating is suitable for use as a protective finish, the salt spray test accelerates corrosion by subjecting the coated samples to a corrosive attack. The appearance of the corrosion byproducts (oxides) is assessed. The duration of the test depends on how resistant the coating is to corrosion.
When compared to ACT, standard corrosion testing might take up substantial time blocks. Accelerated testing may, under the correct circumstances, produce information useful in deciding the most corrosion-resistant materials for an application.
Accelerated Corrosion Testing Method
For accelerated corrosion testing, the samples are tested for salt spray by being placed in an ASTM B117-compliant test chamber that is operated under the circumstances outlined in ASTM B117.
Pure sodium chloride is dissolved in pure water at a weighted ratio of 5% sodium chloride to 95% water to create the test solution that will be sprayed. Purity requirements for each solution should follow the ASTM B117 standard. The test chamber should be pre-conditioned to operate at a temperature of 35°C. Utilizing a minimum of two 80 cm2 funnels, each placed in a measuring cylinder graduated in milliliters, the salt fog fall-out rate is confirmed. Collectors are positioned inside the chamber, one near the atomizer and one away from the atomizer, nominally at the same height as the test samples, in line with the placements described in ASTM B117, while also taking into account the work space designated by the chamber maker.
Video 01: Demonstration of an accelerated corrosion test
Common Uses of Accelerated Corrosion Testing
- This test can be performed to determine how resistant coated and uncoated metallic specimens are to corrosion when exposed to a salt spray environment at a high temperature.
- To evaluate various metals’ or coatings’ levels of corrosion resistance.
Advantages of Accelerated Corrosion Testing
- You can assess the appropriateness of coatings, paints, and metals to resist corrosion or exposure to maritime environments after an ASTM B117 corrosion exposure.
- You may determine how effectively a coating adheres to metal and how far the corrosion has advanced by using ASTM D3359 (adhesion with tape), in addition to the corrosion test.
- You can examine how corrosion progresses from a scratch through the paint or coating to the underlying metal by adding ASTM D1654 (scribing) to your analysis.
Disadvantages of Accelerated Corrosion Testing
- Salt spray tests do not provide good results for the outdoor service performance of coatings.