Change of pH in corrosion chamber

In summary, a new forum member is seeking help with their use of a corrosion chamber and their issue with the pH dropping during the neutral salt spray test. The expert explains that this is likely due to the atomization of the NaCl solution and the change in temperature, and suggests potential solutions to address the issue.
  • #1
stagger lee
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0
Hi all. New to the forum & 1st post.

I've recently been put in charge of using a corrosion chamber (Ascott 450+XP) in my place of work and I've not had much experience using them.

We are validating the equipment to BS EN ISO 9227:2006 (pretty much exact same as ASTM B117) using steel plates and subjecting them to a neutral salt spray test for 48 hours at 35°C.

The problem I'm having is when monitoring the fallout collection the pH seems to be becoming more acidic. The pH prior to entry to the chamber was 6.9 (should be between 6.5 & 7.2 according to standard) but when I am measuring it from the external fallout collectors it is dropping to just over 5.0.

I imagine it has something to do with atomisation of of the NaCl solution or the temperature change but I am not 100% certain.

Would any of you good people be able to shed some light on this for me please?

Many thanks in advance.
 
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  • #2


Hi there, welcome to the forum! I am a corrosion expert and I'll do my best to help you out with your question.

First of all, congratulations on taking on the responsibility of using the Ascott 450+XP corrosion chamber. It is a powerful and widely used tool for corrosion testing, and it's great that you are validating it to the BS EN ISO 9227:2006 standard.

Now, to address your issue with the pH dropping during the neutral salt spray test. You are correct in thinking that it is likely due to the atomization of the NaCl solution and the change in temperature. When the salt solution is atomized, it can create an acidic mist that can lower the pH of the fallout collection. Additionally, the increase in temperature can also contribute to the decrease in pH.

To confirm this, you can try running the test with a different type of salt solution or adjusting the temperature to see if it affects the pH. It may also be helpful to consult the manufacturer's instructions for the corrosion chamber to see if there are any specific recommendations for controlling the pH during testing.

I hope this helps. Let me know if you have any other questions or concerns. Best of luck with your testing!
 

1. What is a corrosion chamber?

A corrosion chamber is a controlled environment in which materials are exposed to corrosive agents to simulate and accelerate the process of corrosion. It is commonly used in scientific research and industrial applications to test the durability and corrosion resistance of materials.

2. How does the pH level affect corrosion in a corrosion chamber?

The pH level is a measure of the acidity or alkalinity of a substance. In a corrosion chamber, a change in pH can affect the rate and severity of corrosion. Low pH levels (acidic) can accelerate corrosion, while high pH levels (alkaline) can slow down or even prevent corrosion.

3. What factors can cause a change in pH in a corrosion chamber?

A change in pH in a corrosion chamber can be caused by various factors, such as the type and concentration of corrosive agent, temperature, and exposure time. Other factors that may contribute to a change in pH include the presence of other chemicals or contaminants, and the type of material being tested.

4. How is the change of pH measured in a corrosion chamber?

The change of pH in a corrosion chamber can be measured using a pH meter or pH indicator strips. These tools provide a numerical value or color change that indicates the level of acidity or alkalinity in the chamber. Regular monitoring of pH levels is important in determining the progress and severity of corrosion in the materials being tested.

5. How can the pH level be controlled in a corrosion chamber?

The pH level in a corrosion chamber can be controlled by adjusting the concentration of the corrosive agent, adding neutralizing agents to counteract the acidic or alkaline effects, or changing the temperature and exposure time. It is important to maintain a consistent pH level in the chamber to accurately study the effects of corrosion on materials.

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