2020 -12 -15 By Industrial Chain Expert

Anti-Corrosion Chain Testing Standard - Salt Spray Test

| Why does the chain need to do the salt spray test?

Carbon steel chains have good strength and wearing resistance. However, in corrosive environment, the chains are easily got rusted. Most of the corrosion is caused by the exposure to atmospheric environment, and the most common and destructive is salt spray corrosion.

With the advancements in metal anti-corrosion technology, MCC has introduced various anti-corrosive coatings, including nickel plated, zinc plated, GN, CRF coatings and so on.

To assess the protection ability of coating against the corrosion, a testing method that is fair and close to corrosive condition of natural environment is necessary.

Since salt spray corrosion is the most common factor lead to rusted metal, scientists have developed Salt Spray Test (SST) to simulate the severely corrosive condition and examine the rusted process. Currently, the salt spray is one of the most widespread corrosion testing methods.

Extended Reading

Comparing Anti-rust Chains - Find Out the Most Suitable Application

| Salt Spray Testing Standard

The standards clearly stipulate the information to carry out the test, such as temperature, moisture, concentration of salt water (sodium chloride, NaCl), pH, etc. Also, the salt spray test machine is required to be manufactured according to the standard.

ASTM B117 and ISO 9227 are both commonly adopted international standard for salt spray testing. MCC has adopted ASTM B117 standard.

ASTM B117：ASTM B117 standard is developed by American Society for Testing and Materials. It was supposedly used as early as 1914 with roots in the National Bureau of Standards, originally published in 1939 by ASTM, and became a standard from 1962. ASTM B117 is the oldest and the most widely used standard.

ISO 9227 : ISO 9227 standard is developed by International Organization for Standardization. There are some differences between ISO 9227 and ASTM B117. It is more commonly used in European countries.

	ASTM B117	ISO 9227
Density, g/cm3	1.024286-1.037261@25°C	1.029-1.036@25°C
Mass of NaCl required per 1 L	53 ± 10.6 g	50 ± 5 g
Electrical conductivity	Max 5.0 µS/cm at 25°C	Max 20 µS/cm at 25 °C ± 2 °C
Allowable Limits for Impurity Levels in Sodium Chloride	Total impurities ≦0.3% Halides (bromide, Fluoride and iodide) ≦0.1% Copper < 0.3 ppm Anti-caking agents none added	Total impurities≦0.5% Copper +Nickel +Lead≦0.005%(50ppm) Sodium iodide≦0.1% Anti-caking agents none added
Specimens suspended angle	15-30°	15-25°
Salt concentration	5%
pH range	6.5 to 7.2
Temperature	35 +/- 2°C
Atomization and Quantity of Fog	For each 80 cm2 of horizontal collecting area, there will be collected from 1.0 to 2.0 mL of solution per hour.

| Salt Spray Testing Method

1. Pictures of salt spray machine

鹽霧試驗機

During salt spray testing

2. Working principle of salt spray test machine

The salt spray test equipment is constructed as a "tower airflow spray device". The spray nozzle adopts "Bernoulli's principle" to provide compressed air from an external air source. The high-speed airflow, which is generated by spraying from the nozzle, forms a siphon and pulls the salt solution into the chamber through an atomizer. Atomized salt fog is sprayed upwards and fill in the chamber.

| Salt Spray Test Result

※ Nickel plated coating testing result

| Application

Ensure the quality of anti-corrosive coating : Make sure chains’ anti-rust performance reach the standard.
Improve the anti-rusted performance: When improving the anti-corrosion coating, salt spray is used to find the best process.
Develop new coating : With the continuous development of corrosion resistant technology, salt spray test is the best method to examine the performance of new coating..
Examine the chain lubricant protection against corrosion

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