You might have heard the term salt spray test quite before. But do you know what that actually means? Even if you don’t know it, we are here to help you before the end. But before that, tell us, how often have you seen metal corrosion? It may be multiple times. It is one of the biggest threats to metal. Well, this is a natural process that you can avoid using a protective layer. You got it right! That’s why metals are often coated with another layer to minimize the redox reactions. Now, just imagine, what if this layer is not capable enough? The metal is still subjected to corrosion. Here’s where salt spray testing comes to the rescue. Let’s learn more about salt fog testing and its process.
First, What is Salt Spray Testing
Let’s start the blog by understanding the meaning of the salt spray fog test. What is salt spray testing? Salt spray testing is a scientific test that checks the capability of the protective shield. The main principle of salt fog testing is that it can assess the consistency of surface coating. Now, you might be wondering, what is the actual process? In the salt fog test, the metal with the coating is subjected to 37 degrees Celsius. The salt spray then helps in evaluating the product and its qualities. The results are shown when the metal protective membrane is exposed to continuous fumes of sodium chloride. Now, the real question is how you can conduct the test.
Things You Must Know Before Starting Salt Spray Tests
Before you start salt spray tests, here are a few things you must know.
- Salt fog testing is generally done in the laboratory, keeping all safety standards in mind.
- Before placing the sample in the test, ensure it is 100% clean. The surface should be processed to ensure it doesn’t interfere with the test.
- Always cross-check the concentration of the solvent in the chamber for effective results.
- Ensure that the sample is removed from the chairman after the exposure time. This will maintain the product’s effectiveness. The length of salt spray testing depends on the metal and desired corrosion resistance.
- In the test chamber, properly mount the samples to ensure even exposure and prevent failures.
- Always follow standard guidelines or regulations to match your test results. The best standards are ISO 9227 or ASTM B117, which provide detailed instructions for the process. Accurate standards are responsible for consistent and accurate results.
- According to industry standards, the mist’s volume shouldn’t exceed more than 5 ml.
Factors Affecting Salt Spray Testing
Different factors affect the results of salt spray testing. Here is the list of these influencing factors:
Relative Humidity
The main factors are relative humidity and temperature. In general, relative humidity should be around 70%. Relative humidity significantly impacts concentration, which shares an inverse relationship.
pH of the solution
Next comes the pH of the solution. The higher the pH, the higher the acidic concentration, and the more corrosive the environment is. However, you must maintain the ideal pH since it keeps on changing.
Test Temperature
The next influencing factor is the test temperature, which is directly proportional to the salt mist corrosion rate. The ideal temperature is 35 degrees Celsius, but any extremely high or low temperature is not suitable for the experiment.
Salt Spray Deposition
Another factor that defines the salt spray test is the deposition amount. The denser salt spray particles can form a maximum surface area, allowing more oxygen adsorption. In simple words, the fine particles result in greater corrosion. In the same way, the salt spray method also has a role, as it affects the composition of salt spray.
Sample Placement
It’s also about the sample placement. Sample placement determines the spray direction, impacting the corrosion and its intensity.
Salt Solution Concentration
Another thing is the salt solution concentration. The concentration decides the corrosion rates based on the material of the protective layer. For example, the corrosion of zinc or copper increases with solution density.
Procedure for Salt Spray Test
Now comes that major question: what is the correct procedure for salt spray testing? Here are the steps you must follow to ensure your experiment is successful. In general, the salt spray test is classified into two steps. The first involves cleaning, and the second is monitoring. Now let’s see these steps in detail:
Start With Sample Preparation
Start the process by cleaning the sample. Remove the metal sample’s dirt, dust, grease, and other pollutants. You should also mask the area you don’t want to expose to the salt fog.
Prepare Salt Solution
Now comes the main step: preparing the salt solution for the salt testing. Here’s what you need to follow:
- Prepare a 5% sodium chloride (NaCl) solution using deionized water.
- Ensure a balanced pH ranging, typically between 6.5 and 7.5, to keep the solution neutral.
Setting the Chamber
A chamber plays an important role in the salt mist test. Make sure that you buy the best quality salt spray test chamber. Keep all the samples in the salt spray chamber above their designated positions. Control the temperature of the environment around 35 degrees Celsius.
Execute
Here comes the most exciting step of the test, i.e., execution:
- Start the chamber or generation system. You will see a continuous mass of sodium chloride in the chamber.
- Throughout the test, maintain the temperature control and monitor the chamber conditions. At the same time, balance the spray pressure.
Note if the sample is developing any significant signs of corrosion.
Examination
Once the test is done, remove the sample from the chamber within the desired duration. Clean the chamber and sample with clean water to remove any residue. Take a brief note about the corrosion, noting its intensity and patterns. Use the set standards to identify and compare the types with the acceptance criteria.
Precautions
For every test procedure, there are some precautions that you must keep in mind:
- Don’t interfere with the chamber until the test is complete. Don’t open or disturb it to ensure safety from fumes, but this may result in inaccurate test observations.
- Maintain the optimal distance between the chamber walls and the metal specimen. If you keep the metal quite close to the wall, it may result in excessive heating.
- Don’t open the chamber directly with your naked hands. Rather, use purging. Allow saline fog to settle down before opening it to the surroundings.
- Control the fog collection beaker to maintain optimal fog inside the chamber.
What are the Applications of Salt Spray Test
Now you know that the salt fog test is a corrosion checker. It helps stimulate the environmental effect of metal in long-term exposure. Here are the common industrial applications of salt mist tests:
- The effectiveness of machine parts used in marine, aerospace, and defense is determined using the same technique. OEM manufacturers also use the same technique to determine the effectiveness of their machine parts.
- To examine the longevity of the materials in all kinds of surroundings.
- To evaluate the metal resistance to corrosion under the high effect of salt water and air.
Different Types of Salt Spray Tests
Different salt spray tests are used to serve unique purposes. These types are different in terms of methodologies and approaches. Here are a few types, along with their explanation:
| Type | Purpose |
| Neutral Salt Spray Test | Perfect to measure corrosion in all industries |
| Acetic Acid Salt Spray Test | Majorly used in automotive |
| Cyclic Corrosion Testing | A rigorous type used to simulate real-world environments |
| Kesternich Test | The chamber used sulfur dioxide to create acidic environments |
| Prohesion Test | Perfect for long-term exposure |
| SCAB Test | Helps to assess metal durability under weather extremes |
| SSC Test | Simultaneous exposure combining saline mist and sulfur dioxide |
| Salt Fog Testing with UV Exposure | Combine the effect of salt fog and sunlight |
Advantages of Corrosion Testing
Now that you know everything about corrosion testing, let’s understand its importance. Why is salt spray test important, and why do manufacturers use it? Here are the key benefits of the salt mist test for manufacturers:
Product Durability
The best thing about testing is that it ensures product durability. The metal protective sheets that undergo the salt spray test ensure that products last longer than expected. Testing also saves customers time and enhances brand worth.
Affordable
While the salt spray test may have an expensive setup, it is affordable in the long term. Testing the products at the start avoids extra costs and market recalls in later stages.
Versatility
Salt spray testing is versatile and can be used on a wide range of metals. It is also affordable, making it reliable in the long term.
Better Products for the Real World
Salt spray testing identifies the finest protective coatings for different metals. Moreover, the test replicates harsh environments, which decide the results.
Which is the Best Salt Spray Test Chamber?
If you are looking for a premium salt spray test chamber for your experiment, consider the one from OTS Technik. The brand offers the finest chambers adaptable to all kinds of metals without compromising consistency.
Way Forward
There’s no doubt that the salt spray test is a crucial tool for humankind. For the entire process, the most important application is a salt spray chamber. With the right steps and measures, you can use the test cycle to identify the strength of the protective shields. This is a simple process that can meet all the test requirements. But remember to follow all the precautions and safety guidelines in salt spray testing labs to ace this quality test.