Investigating critical HVAC failure from ant nest corrosion
Loss of refrigerant liquid caused by "ant nest corrosion"
Recently, one of our customers in the Heating, Ventilation and Air Conditioning (HVAC) industry noticed a leakage of the refrigerant liquid inside a refrigeration unit. We discovered that the micro leak was in one of the finned tubes of the heat exchanger pack made of copper and painted aluminum fins.
Very early in the examination process, our experts in damage analysis suspected a case of ant nest corrosion. A frequent cause of this type of corrosion is the presence of substances that derive from the use of synthetic lubricants or organic products used in the forming and bending phases of copper pipes which in the long term seriously compromise the characteristics of the base material.
Methods for evaluating HVAC failure
Thanks to its specialized technicians, Element has a high degree of expertise in the HVAC sector and a consolidated track record of cases that constitute a solid background in the interpretation of defects and the definition of root causes.
Among the activities that Element performed in this application case were:
- Macrographic examinations for the determination of the penetration of the brazing alloy
- Micrographic examinations to evaluate the microstructure of the materials used and identify any defects or criticalities from which the component may be affected.
- Microanalysis by Scanning Electron Microscope with EDS microprobe to identify potentially aggressive elements.
- Chemical analysis utilizing optical emission spectrometer (OES), ICP-OES, combustion analysis (for the determination of C, S, N, H, and O), IR spectrophotometer, and ion chromatography to verify if the chemical composition of the materials used is acceptable according to international standards and if the process liquids comply with what is declared in the technical data sheets.
A case of “ant nest corrosion”
One of the most critical issues that can be found in copper alloys which are widely used in the HVAC sector is “ant nest corrosion” a phenomenon characterized by interconnected micro-cavities with compact copper oxide inside. This kind of corrosive phenomenon is triggered by the chemical reaction of an organic acid (present inside the pressurized system or in the external air) with oxygen and water.
We were able to identify the cause of the HVAC failure that led to the puncture of the component and the consequent leakage of coolant inside the refrigerant circuits for our customer.
The Element Advantage
Element Materials Technology supports customers in the HVAC industry and equipment manufacturers by performing material characterization tests and failure analysis to determine the causes of component failure or malfunction and take corrective action to eliminate the source of failure.