In the last article about the powder coating process to produce Daiwa Color Pipe and Daiwa Powder Coated Pipes, we mentioned Standard JIS H 8502 for experimental salt spray test. In this post, we will explain how we perform the corrosion resistance test to evaluate the performance of Daiwa Color Pipes.
What is Standard JIS H 8502 for Corrosion Resistance?
JIS H 8502 is the standard set out by Japan Industrial Standard for Methods for Corrosion resistance for Metallic coatings. This standard applied for products coated with metal or plating, either by electroplating, electroless plating, vapor plating and hot-dip plating.
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For each test method, the standard clearly regulates the test specimen, test condition, test duration, judgment results.
Let's delve deeper into The Salt Pray Cycle Test Conducted for Corrosion Resistance in this article.
How is The Salt Pray Cycle Test Conducted for Corrosion Resistance?
Based on the corrosion resistance test method for plating of JIS H 8502, we are conducting the "Cyclic neutral salt spray test method" test. This "Cyclic neutral salt spray test method" is conducted to check the corrosion resistance of plating by repeatedly exposing it to a neutral sodium chloride solution, drying, and wetting the atmosphere in sequence using a neutral salt spray cycle test device. The samples were tested up to 90 cycles.
The order of preparation of the test liquid, the equipment, the position of the test specimen in the test tank, the test conditions, etc. shall conform to this test method.("Cyclic neutral salt spray test method").
Cycle test method (Corrosion Resistance Test)
Test method :「JIS H 8502. Corrosion resistance test method for plating」
Testing machine ： Combined Cyclic Test Machine CYP-90L
Test cycle number： The correlation between cycle tests and exposure tests was carried out with reference to the following literature.
Each cycle : Salt spray (35℃ x 2 hours) → Dry (60℃ x 4 hours) → Wet (50℃ x 2 hours).
We conducted the salt spray cycle test on 3 test samples with the same condition. The 1st test sample 1 color pipe made of galvanized steel, the 2nd test sample is color pipe made of mild steel, and the 3rd sample is bare galvanized steel pipe without resin coating.
Below are the results of salt spray recycle test in laboratory environment. The sample of the bare galvanized steel pipe appears white rust after 9 test cycles, then yellow rust after 60 test cycles.
The sample of the color pipe made of mild steel appears yellow rust at the cut edges where there is no resin coating after 60 test cycles but the surface with coating is not rusted. The sample of the color pipe made of galvanized steel does not appear any sign of rust after 90 test cycles.
Interpreting the cycle test result to the durability in real life based on the table below
From Durability test of surface-treated lightweight section steel for architectural structures. According to the table below, Daiwa Color pipe passed 90 test cycles, which represents 20 years in coastal areas or 30 years in countryside areas.
Architectural Institute of Japan Conference Academic Lecture Collection "Experimental Research on the Structure and Durability of Steel Houses" (Part 11. Durability test of surface-treated lightweight section steel for architectural structures)
What is The Result of The Real Exposure Test for Corrosion Resistance?
Experiment on Daiwa Color Pipe and Bare Steel Pipe
This test is carried out when we put the samples of Daiwa Color Pipe and bare steel pipe outdoors in an open space under sunlight and rainfall in the atmospheric environment for a long period of time to see how rust and oxidation developed on the surfaces of those samples.
We put cut samples of Daiwa Color pipes and bare mild steel pipes on the shelf at the same time from 22/Feb/2024 to 08/Oct/2024. The samples were exposed to changing weather conditions in Ho Chi Minh Vietnam with strong sunsight and hot temperature up to 36 degree Celsius from January to April, then under rainfall and high humidity of the rainy season from May to October.
After more than 9 months, the results are observed as below. The samples of mild steel pipes are heavily rusted due to oxidation. We can spot the red rust everywhere around the samples.
The samples of color pipes still have a shining surface without any rust, except the cutting edges have slight rust due to no protection of powder coating, and no painting.
The results above highlight the correlation between the cycle test and the exposure test. They demonstrate that the Daiwa Color Pipe powder coating significantly enhances corrosion resistance, extending the lifespan of the products for several years compared to bare mild steel or galvanized pipes.
Please contact us if you want to test the durability of Daiwa Color Pipes.
Conclusion
Generally, metal materials are surface-treated with plating or painting to prevent rust, but rust may occur if used for a long time.
The salt spray cycle test is designed to accelerate corrosion under conditions that closely mimic the actual usage environment of the product. This test evaluates the corrosion resistance and rust prevention properties of both inorganic and organic plating and painted films on various metal materials. By comparing the occurrence of corrosion and discoloration of the samples before and after the test, it allows for a compressed evaluation of corrosion behavior that typically occurs over an extended period.
The real exposure test is a method used to verify and confirm the results of the cycle test regarding the weather resistance and corrosion resistance of plating products. The occurrence of weight loss due to corrosion, rust, swelling, and discoloration is observed and investigated by comparing different samples under the same testing conditions and duration.
Through these tests, it is concluded that Daiwa Color Pipe is exceptionally good at weather resistance and corrosion resistance, making it suitable for applications that require durability in harsh corrosive environments, such as heavy industrial areas, urban areas, and coastal regions. It is ideal for underground immersion anti-corrosion pipes and winding shafts in agricultural greenhouses.
