A review on ASTM B117- Standard Practice for Operating Salt Spray (Fog) Apparatus
Definition
Salt spray test is a standardized, widely recognized corrosion test method. It served as an evaluation method for the corrosion resistance of materials and surface coatings.
Test Standard
ASTM B117- Standard Practice for Operating Salt Spray (Fog) Apparatus. First published in 1939. As stipulated in Australian Standard AS3566.2- Self-drilling screws for the building and construction industries Corrosion resistance requirements. ASTM B117 is one of the test standard to classified different anti corrosion coating class used for self-drilling screws.
Extract from ASTM B117
Objective
To evaluate the suitability of the coating for use as a protective finish on applied material. Usually applied on metallic substances.
Terminology
By producing a corrosive medium to coated samples in a controlled environment for a pre-determined period of time. Corrosive medium in this test shall be the salt solution and the controlled environment the salt spray chamber.
Condition of the test chamber:
Test specimen: Screws with anti-corrosion coating
Salt solution concentration: 5% NaCl + 95% Reagent water.
(In comparison normal sea water salt content range 1.8%-3%)
pH range: 6.5- 7.2 at 35°C
Solution condition: Atomized into uniform droplets
Extract from ASTM B117
Result Evaluation
The appearance of corrosion products (rust and oxides) are evaluated after a pre-determined period of time. The period of exposure shall be agreed beforehand between purchaser and seller.
Extract from ASTM B117
Result Derivation
The higher the corrosion resistant the coating is, the longer the period of testing before failure.
Advantage of Salt Spray Test
The standard is comprehensive, inexpensive and reasonably repeatable. Mostly deploy as quality control role to audit the surface treatment process, to access the quality of coatings and serve as a guideline to ensure the stability in the chemicals coating process.
Disadvantages of Salt Spray Test
The result has little application in predicting how materials or surface coatings will resist corrosion in the real world as it only factors in high chloride attack without other accelerated real-world corrosive conditions.
Extract from ASTM B117
Conclusion
Though predicting the durability of an anti corrosion coating based solely on salt spray test results lack credibility, it is undeniable serves as a guideline and reassurance of the coating quality itself and also the quality control of the surface treatment process. This plays a crucial part to ensure consistent and reliable performance of the coating material. After all, quality consistency is the main key in ensuring high quality, reliable product in manufacturing.
Fiable manufactures anti corrosion fasteners, adopting stringent regulations stipulated in ASTM B117 to ensure the quality of the coating material and the surface treatment process in order to deliver the finest premium fasteners.
By consisting of 3 coating class to cater different customer’s requirement and usage condition, our anti corrosion fasteners can deliver the desired anti corrosion results end users seek, ability to perform even in the harshest environment.
Reach out to our coating specialist today to discuss your options!
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