Ask the chemist – Foaming in A/C compressor oils: causes and explanations

1. The market is witnessing an increasingly recurring issue regarding the interaction between additives and lubricants. What does this involve?

The market (particularly in the automotive sector) is complaining about foaming in A/C compressor oils following the insertion of solvent-based additives or tracers.

2. What are the causes of foam in oils?

Foam is a group of small bubbles of refrigerant gas that accumulate on or near the oil. The presence of air bubbles in the fluid can lead to excessive oxidation, and cavitation, and reduce the lubricating properties of the oil, resulting in system failure.

The main causes of foam in oils are:

• contamination with water, solvents and solid particles;
• mechanical problems and/or incorrect setting of the system (unsuitable suction temperatures and too high or too low operating pressures);
• cross-contamination of the fluid with the wrong lubricant;
• depleted anti-foaming agent (because not enough or altered by other additives);
• anti-foaming agent placed in excess.

To solve this foaming problem, we must necessarily identify its primary cause. This process cannot be limited to the visual observation of the phenomenon but requires in-depth investigations and verifications carried on by accredited laboratories.

3. This phenomenon occurs more often in the automotive industry. Why?

This is because the interaction between solvent-based additives (particularly common in the automotive sector) and the lubricant compromises the stability of the anti-foaming additives contained in the A/C compressor oil.

More precisely, solvent-based additives prevent the proper functioning of the anti-foaming agent and, more importantly, reduce the viscosity of the oil, affecting the whole system.

Proof of this is the fact that elements commonly contained in additives (calcium, magnesium, boron, molybdenum, phosphorus, sulphur, etc.) get found in the A/C compressor oil.

4. Why has this problem never occurred with Errecom additives/lubricants?

There are many types of additives that, when mixed with base oils, improve their properties and eliminate unwanted ones.

Additives can either be organic or inorganic compounds, dissolved or suspended as solid particles in the oil and have three roles.

• Improving the properties of the oil with antioxidants, corrosion inhibitors, anti-foaming agents and demulsifiers.
• Eliminating unwanted oil properties with pour point reducing agents and viscosity index improvers.
• Adding new properties to oils with extreme pressure (EP) additives, detergents, metal deactivators and emulsifiers.

As a manufacturer of lubricants and additives, Errecom is fully aware of their interactions and, therefore, can guarantee that their combined use does not give rise to this type of problem. All our additives do not alter the original characteristics of the A/C compressor oil.

Specifically, Errecom additives are:

• solvent-free, thus ensuring less water and/or contaminants into the oil wherein they are added
• perfectly miscible with all the lubricants on the market
• capable of preventing foaming in oils and reducing the surface tension to accelerate the foam collapse.

5. How to choose the most suitable after-market additive to restore the oil’s original performance?

Additives play a key role in guaranteeing the efficiency of a system over time and, consequently, reducing its consumption.

To choose the most suitable additive, I suggest relying only on manufacturers whose professionalism is recognised by the market, always remembering that those who formulate refrigeration lubricants perfectly know what air conditioning and refrigeration systems need.

Also, do not use solvent-based products: additives must only be carried by the lubricant so that they do not affect the one that is already in the system.

Carefully follow the instructions for use: dosage and procedure are essential to achieve the result.

Last but not least, determine the system’s actual problems: acidity, refrigerant gas leaks, oil fouling, etc. Never forget that different problems require different solutions.