Failure investigation of Cu-DHP tubes due to ant-nest corrosion

摘要

Purpose - The purpose of this paper is to address the main aspects of ant-nest corrosion failure mechanism of a Cu tube in heating ventilation and air-conditioning (HVAC) installations and analyze the possible root causes through various case studies presented. Design/methodology/approach - Failure investigation process includes mainly stereo-, light optical and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy for elemental microanalysis, as the main analytical techniques for material characterization and root-cause analysis. Findings - The investigation findings, obtained from corrosion products' analysis in conjunction to metallographic evaluation in transverse sections, illustrate the principal characteristics ("fingerprints") of ant-nest (formicary) corrosion mechanism. Originality/value - This paper which deals with the presentation of applied failure analysis/case histories' investigation, summarizing the main aspects of an important and insidious type of Cu corrosion, taken place in HVAC installation systems and, on the other hand, presenting a complementary analysis of the chemical processes involved in the progressive failure mechanism constitutes an integrated approach, aiming to become a concise contribution to this subject.