Auto A/C Terms - Glossary
Corrosion in Auto A/C Systems

Corrosion in auto A/C systems is one of the leading causes of A/C systems failures. Corrosion, which is nothing more than the eating or wearing away of the A/C components in the system, is usually caused by the formation of harmful acids in the A/C system.

Acids form in the A/C system when moisture mixes with refrigerants. Understand that automotive systems have a far greater possibility of moisture contamination then commercial or residential A/C systems because automotive systems include flexible rubber hose sections. It is that rubber hose that allows moisture to enter the system. However, understand that the moisture only passes through the hose at the molecular level.

Once inside the A/C system, the receiver drier or accumulator are intended to trap and hold that moisture. More times than not, the desiccant or drying agent in the drier or accumulator is already contaminated and unable to hold any more moisture. When that happens, the moisture is left to mix with the refrigerant.

When moisture and refrigerant mix, the resulting chemical reaction causes harmful acids to form. Those acids circulate throughout the system and begin to corrode aluminum components like the condenser and evaporator. Leaks in the condenser and evaporator are usually noticed first because they are manufactured from the thinnest metals.

However, the bigger problem is that the corrosion creates particles of debris. That debris is circulated throughout the system and begins to plug up or restrict other components like the orifice tube or expansion valve. When that happens, the flow of refrigerant and A/C compressor oil is restricted. Continued restriction in the flow of refrigerant and oil quickly leads to a failure of the A/C compressor.

For that reason, it is important to maintain a dry system. That can be accomplished by assuring a proper vacuum whenever A/C service is performed and be sure that driers or accumulators are replaced at least every four years. You should also make it a habit to check the orifice tube whenever servicing the A/C system. The orifice tube is your best indication of the condition of the system.