 |
| Example of a well designed all-aluminium brazed heat exchanger |
The corrosion rate of aluminium is very low when exposed to most environmental conditions, because aluminium is protected by a stable oxide layer. When corrosion does occur, it is typically due to poor design against corrosion. In a multi-material/alloy system where the materials are in direct contact, such as a heat exchanger or liquid lines, corrosion will take place on the most sacrificial part - the less noble part.
Hence, it becomes essential to consider that the galvanic series become important. It is no surprise to see corrosion developing in a copper tube-aluminium fin heat exchanger, due to high electric potential difference. Aluminium as a stand-alone tube, when selecting the proper alloy, is resistant to even the aggressive environment, like sea water conditions.
|
|
| Macro photo of conventional copper tube-aluminium fin heat exchanger before and after one year in a coastal Florida environment! |
Unlike conventional HVACR coils, all-aluminium heat exchangers are made entirely of aluminium. This “one-metal” concept eliminates galvanic currents that are generated when different metals touch in conventional coils. Many comparative tests, including the salt mist and ammonium sulphate test, provide proof of the increased corrosion resistance of all- aluminium heat exchangers.
Conclusion: Well-designed all-aluminium heat exchangers offer three-and-a-half times higher corrosion resistance than copper/ aluminium coils.
