Configuration-dependent galvanic corrosion of carbon steel in inhibitor-treated cooling water: evidence from long-term service exposure

• G.R. Sunaryo¹, R. Kusumastuti², D.S. Wisnubroto³, Sriyono¹, D.T. Jatmiko⁴, F.Y. Sulistyo¹ and N. Luhur⁴

¹ Research Center for Nuclear Reactor Technology, Research Organization for Nuclear Energy, National Research and Innovation Agency (BRIN), South Tangerang 15314, Indonesia
² Research Organization for Nanotechnology and Materials, National Research and Innovation Agency (BRIN), South Tangerang 15314, Indonesia
³ Research Center for Radioactive Waste and Nuclear Fuel Cycle Technology, Research Organization for Nuclear Energy, National Research and Innovation Agency (BRIN), South Tangerang 15314, Indonesia
⁴ Directorate of Nuclear Power Facility Management, National Research and Innovation Agency (BRIN), South Tangerang 15314, Indonesia

Abstract: Understanding long-term corrosion behavior of carbon steel in inhibitor-treated cooling-water systems requires considering not only bulk water chemistry but also electrochemical interactions between dissimilar metals. This study investigates the crystallographic characteristics of corrosion products formed on carbon steel after prolonged service exposure under chemically compliant cooling-water conditions, with particular emphasis on galvanic coupling with stainless steel. X-ray diffraction (XRD) analysis reveals the formation of thin, nanocrystalline iron-oxide layers, indicating effective suppression of uniform corrosion by inhibitor-based chemistry control. However, pronounced differences in peak broadening and structural disorder are observed between galvanically coupled regions, electrically coupled but non-contact areas, and galvanically isolated surfaces. These differences suggest that galvanic interaction is the dominant factor controlling corrosion-product evolution. Specimen orientation further influences oxide retention through hydrodynamic effects, acting as a secondary modifier. The results show that while inhibitor-treated water establishes a stable baseline corrosion regime, it is insufficient to eliminate localized galvanic degradation in mixed-metal systems. These findings provide rare long-term, service-derived evidence linking inhibitor performance, galvanic coupling, and corrosion-product crystallography, highlighting the need to explicitly integrate galvanic coupling considerations into corrosion and scale inhibition strategies in industrial cooling-water environments.

Keywords: cooling water system, corrosion inhibitor, galvanic coupling, carbon steel, X-ray diffraction, corrosion products

Int. J. Corros. Scale Inhib., 2026, 15, no. 2, 143-155
doi: 10.17675/2305-6894-2026-15-2-9

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