Marcelle de Waal, a senior consulting engineer at One Eighty Materials Engineering Solutions, highlighted the crucial role of water quality in preventing heat exchanger corrosion. One Eighty offers comprehensive services, including forensic analysis, material testing, and water quality analysis, often addressing the significant financial impact of heat exchanger failures.
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De Waal explained that heat exchangers, used across various industries, are susceptible to corrosion primarily driven by water chemistry. Key parameters include pH (with a narrow ideal range), electrical conductivity, and specific elements like ammonia (corrosive to copper), chlorides (aggressive towards stainless steel), calcium (causing scale), and iron content (accelerating galvanic corrosion). The most aggressive corrosive agents vary depending on the material; chlorides pose a major threat to stainless steels, while ammonia is detrimental to copper alloys. Elevated iron content exacerbates issues in bimetallic systems.
Out-of-spec parameters lead to various issues: pH deviations cause pitting, high electrical conductivity increases galvanic corrosion, and specific elements like sulphur, ammonia, and nitrates weaken protective layers. Case studies demonstrated severe consequences, such as ammonia-induced stress corrosion cracking (SCC) in copper and failures from freeze-thaw cycles.
A common oversight, de Waal noted, is relying solely on potable water standards, which are insufficient for heat exchangers. One Eighty’s expertise lies in interpreting manufacturer-specific water requirements and conducting targeted analyses. She also discussed dissimilar metal corrosion, stressing the importance of selecting compatible materials based on the galvanic series to minimise corrosive reactions.
One Eighty’s root cause analysis involves on-site inspections, lab analysis (mechanical, chemical, metallurgical), and comparing findings against OEM standards to identify failure mechanisms. Recommendations often focus on improved water chemistry control, proper welding procedures, and post-weld treatments like pickling and passivation for stainless steels. De Waal stressed the importance of consistent water quality monitoring, material compatibility checks, and regular maintenance to prevent costly failures and ensure the longevity and efficiency of heat exchanger systems.
