Assessment of the Possibility of Galvanic Corrosion in Aluminum Microchannel Heat Exchangers

Abstract

As part of the work, three used microchannel heat exchangers from different manufacturers were analyzed. For comparison purposes, the new heat exchanger was also subjected to the NSS salt spray test. The material of the Al-Si system used for brazing, as well as the material of the core, were subjected to electrochemical tests. In laboratory tests, polarization curves were determined for the Al-Si material used for brazing, as well as for the core material. On the basis of exchanger research, it was found that a critical problem in the use of microchannel exchangers is galvanic corrosion occurring in the areas of brazed joints. Electrochemical tests have shown that the Al-Si alloy used for brazing has a lower value of corrosion potential than the core material. The existing potential difference is sufficient for galvanic corrosion. Electrochemical corrosion is initiated in the eutectic structure. The soplid solution is the anode and is particularly susceptible to corrosion, which led to its preferential dissolution in the entire volume of the eutectic mixture.

Keywords

• heat exchangers
• galvanic corrosion
• microstructure
• electrochemical test
• NSS test
• brazing