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Aluminum corrosion

 

My question is regarding automotive air conditioning evaporators. We are experiencing a rather high failure rate here in Canada. We are trying to determine why, also the metal composition of the evaporator I guess it would be made of an aluminum alloy? If you know the answers to my question that would be great if not could point me in the right direction .

Sincere Regards,

Owen Hayes
- Surrey, British Columbia, Canada

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Owen, there are a number of possible reasons why you would see an increase in the failure rate of aluminum automotive air conditioning evaporators. It may be that the vehicles are operating in an area with a corrosive air pollutant which causes an increase in corrosion. Sulfur dioxide is an example of such a pollutant. It dissolves in the condensation on the evaporates and forms sulfuric acid. This quickly corrode the aluminum evaporator.

Another factor which may be part of this problem are the changes occurring in the manufacturing process of the evaporators themselves. Several changes are being made at this time. The first is that chromate coating are being phased out as corrosion inhibitors on aluminum evaporators as part of an industry goal to eliminate hexavalent chrome from vehicles. The second change that is occurring is controlled atmosphere brazing process is replace vacuum brazing of the evaporators. Either of these changes on their own or in combination could cause the increase in corrosion you are seeing.

If you have more information on the year, make and model of vehicles where the corrosion failures are occurring, I could help to identify the source of the problem.

Roy Nuss
Trevose, Pennsylvania, USA