Should you mix camlock fittings of different materials ?

It is generally not recommended to mix camlock fittings made from different materials. The reason for this is that each material type, the most common being stainless steel, aluminum, brass, and polypropylene, has its own chemical resistance, tensile strength, and temperature range. For this reason, when connecting couplings of different materials, corrosion, uneven wear, and connection issues may arise. For safety and to promote a long service life, it’s considered best practice to use camlocks where both coupling halves are made from the same material.

For this reason, most reliable experts will advise you against combining different camlock materials, such as metal with plastic or brass with aluminum. Although these can lead to issues in the long term, they can still work under certain circumstances, for example, for short periods of time, and longer with the proper care.

 Let's look at this in more detail so an informed decision can be made for your particular application.

Reasons to avoid mixing materials:

• ● Material Compatibility: Different metals can cause galvanic corrosion. This happens with the addition of an electrolyte such as water.* 
• ● Tensile Strength: The weaker tensile strength of plastic could compromise the connection.
• ● Temperature and Pressure Tolerance: Plastic camlocks have a lower temperature tolerance when compared to metal ones; higher temperatures can cause the plastic to soften, which reduces its pressure rating.
• ● Uneven Wear: The wearing surfaces of softer adapters can be affected by being coupled with a harder metal.
• ● Fluid Compatibility: Different materials are designed to handle specific fluids, pressures, and temperatures. Mixing materials can lead to issues if one material isn't compatible with the fluid, its temperature, or pressure. 
• ● Gasket incompatibility: Plastic cams have EPDM gaskets while metal cams have Buna-N gaskets,  both of which are suited to different chemical applications.

* Note: when two coupling halves connect, there is actually no contact between the two different materials of the metals since there is a gasket in between. So when an electrolyte is introduced, the two opposing materials are not in contact. It is only the cam arms that make contact with the outside of the connection. For this reason, it could be argued that the material compatibility of the camlock halves is not an issue when it comes to a mixed connection. However, this does not apply to the gasket, which could still have compatibility issues with the fluid; however, galvanic corrosion between the metals is unlikely since they don't touch in the presence of the fluid being transferred.

Reasons why mixing Stainless steel with Poly is not recommended:

• ● Material Strength Differences: Stainless Steel is an exceptionally strong metal alloy, while Polypropylene is a relatively softer plastic. A mixed connection with these materials will be limited by the strength of the poly, which is softer and does not have the tensile strength of stainless.
• ● Temperature and Pressure Differences:  Stainless Steel has very high temperature and pressure ratings, while polypropylene has a lower tolerance. Exposure to high temperatures causes poly to soften and decrease its pressure-bearing ability
• ● Chemical Compatibility Differences:  Stainless Steel offers excellent resistance to the widest array of chemicals, specifically the 316 grade. Although poly offers excellent chemical resistance to many solutions, it is not suitable for all the chemicals that stainless steel can resist. So if a chemical is being transferred in a system that is compatible with stainless steel but not compatible with poly, then this could compromise the system by leading to corrosion. 
• ● Gasket Material Differences: Stainless couplings are installed with Buna-N Gaskets, and poly couplings are installed with EPDM Gaskets. Making a mixed connection with these two different gaskets could lead to compatibility issues if one of the gaskets is not suitable for the fluid.

Reasons why mixing Stainless steel with Aluminum is not recommended:

• ● Galvanic Corrosion: The most common reason given not to couple a stainless coupling with an aluminum one is galvanic corrosion. This occurs when different metals are in contact and are surrounded by an electrolyte, which could just be water, and the process would cause the aluminum to corrode. However, as mentioned above, this would only occur under a very special set of circumstances and would generally not affect general-use applications too seriously. (For critical applications, it is important to keep the camlock material the same.)
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• ● Why is Galvanic Corrosion unlikely: The reason that galvanic corrosion is unlikely in most situations is because when the male and female camlocks are connected, they are separated by a gasket, so they don't actually touch internally where the fluid is present. If they don't actually touch, then no destructive reaction can occur. The only place they touch is on the outside of the fluid line where the camlock lever arms hold the connection in place, and possibly if the male adapter touches the inside wall of the female coupler once connected. In both these circumstances, the connection points would be very small, and then you would still have to submerge the whole connection in an electrolyte to instigate a reaction. So basically, this would be underwater or a high-humidity situation. And even then, many aluminum camlocks have stainless handles, and they do not react when coupling with other aluminum adapters.
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• ● Chemical Compatibility Differences: There will be certain chemicals that will be compatible with Stainless Steel and not with Aluminum. Stainless steel is corrosion-resistant to a wide range of chemicals, including acids, while aluminum is suited to mild chemicals. In these situations, the aluminum half of the connection could be susceptible to corrosion.

Reasons why mixing Stainless steel with Brass is not recommended:

• ● Galvanic Corrosion: This is also the most common reason given not to couple a stainless coupling with a brass one. This electrochemical reaction occurs when two dissimilar metals are in contact and exposed to an electrolyte, and the process would cause the brass to corrode. However, once again, as detailed above, this would only occur under a very special set of circumstances. (For critical applications, it is important to keep the camlock material the same.)
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•  ● Why is Galvanic Corrosion unlikely? The reason that galvanic corrosion is unlikely is that the two mating camlocks are separated by a gasket. This means they don't touch internally where the fluid (Electrolyte) is present. If there is no contact between the two dissimilar metals, then no destructive reaction can take place. 
• They do, however, touch on the outside of the fluid line where the cam lever arms close on the adapter and lock the connection in place. There is also a chance they touch on the inside wall of the female coupler once the male adapter is connected. In both these cases, the points of connection would be very small, and to entice a reaction, you will still require an electrolyte, which would mean the whole camlock connection would have to be submerged in a liquid or be in a very high humidity situation. 
• ● Chemical Compatibility Differences: Certain chemicals are compatible with Stainless Steel and not with Brass, and this could cause corrosion issues over time. 

Reasons why mixing Aluminum with Brass is not recommended:

• ● Galvanic Corrosion: This electrochemical reaction is also the most common reason given not to couple aluminum and brass camlocks. This process would cause the aluminum to corrode. However, as mentioned above, this is unlikely to occur in general applications. (For critical applications, it is important to keep the camlock material the same.)
•  ● Why is Galvanic Corrosion unlikely? The reason that this chemical reaction is unlikely to occur is that there are no contact points inside the camlock connection where the fluid is. There are small contact points on the outside of the connection; however, these points are small and would also require exposure to an electrolyte to instigate a reaction.
• ● Chemical Compatibility Differences: Certain chemical solutions are compatible with Brass and not with Aluminum, and vice versa, and this could cause corrosion issues over time. 
• ● Material Strength Differences: Brass is stronger than aluminum, so if the connection is subjected to undue stress, then the aluminum is more likely to be compromised.

Reasons why mixing Aluminum with Poly is not recommended:

• ● Material Strength Differences: Aluminum is a metal alloy that is stronger than plastic polypropylene, so if the connection is subjected to undue stress, then the polypropylene is more likely to be compromised.
• ● Temperature and Pressure Differences:  Aluminum has a higher temperature and pressure rating than polypropylene. Exposure to high temperatures causes poly to soften and decrease its pressure rating.
• ● Chemical Compatibility Differences: Certain chemical solutions are compatible with Poly and not with Aluminum, and this could cause corrosion issues over time. 
• ● Gasket Material Differences: Aluminum couplings are installed with Buna-N Gaskets, and poly couplings are installed with EPDM Gaskets. Making a mixed connection with these two different gaskets could lead to compatibility issues if one of the gaskets is not suitable for the fluid.

Reasons why mixing Brass with Poly is not recommended:

• ● Material Strength Differences: Brass is a metal alloy and is significantly stronger than polypropylene. So if the cam and groove connection is subjected to stress, then it is the plastic polypropylene that is more likely to be compromised.
• ● Temperature and Pressure Differences:  Brass has a higher temperature and pressure rating than plastic polypropylene. High temperatures cause polypropylene to soften, and as a result, its pressure rating decreases.
• ● Chemical Compatibility Differences: There are certain chemical solutions that are compatible with Poly and not with Brass, vice versa, and this could lead to corrosion issues over time. 
• ● Gasket Material Differences: Brass couplings are installed with Buna-N Gaskets, and poly couplings are installed with EPDM Gaskets. Making a mixed connection with these two different gaskets could lead to compatibility issues if one of the gaskets is not suitable for the fluid.

Best practices to choose the most compatible fittings:

• ● Match materials: It is considered a best practice to match the materials of your camlock connection. That will entail connecting a stainless steel female coupler with a stainless steel male adapter, a poly coupler with a poly adapter, and so forth. This is particularly important in critical applications.
• ● Consider the application: Consider the fluid, the temperature, pressure, and the mechanical stress present in your application, and choose a material that is compatible with all these variables.

If you have to mix, how to prolong service life:

*NOTE: If this is a critical application or one where human safety could be compromised, then do not consider mixing materials.

• ● Check compatibility: Make sure the fluid is compatible with both cam and groove materials, as well as with the gaskets.
• ● Consult Compatibility Charts: https://www.coleparmer.com/chemical-resistance
• ● Check Temperature and Pressure: Make sure the less robust material can withstand the temperature and pressure of your application. This will most likely involve checking the ratings of the polypropylene half of the connection.
• ● Ensure there is no undue stress on the connection: If the connection is subject to any stress, make sure the less robust material can withstand it; again, this will most likely be the Poly.

In Summary

Mixing camlock fittings made from different materials is generally not recommended. When it comes to material strength, pressure, temperature, and chemical resistance, each material has its own pros and cons. When combining different materials, various issues can arise, such as uneven wear, gasket incompatibility, corrosion, temperature and pressure intolerance, and succumbing to mechanical stress. While some mixed connections may work in low-risk or short-term situations, they are not recommended for critical applications. The best practice is to base the material selection on the fluid being transferred and operating conditions, and then to match the material in both halves of the connection.

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