# Effect of Marine Coolant Additives on Cavitation Erosion-Corrosion of Diesel Engine Cylinder Liner
## 1 Introduction
Recently, studies on cavitation phenomena in fluids using computational fluid dynamics (CFD) have been actively conducted across various fields, significantly enhancing the understanding of the mechanisms and characteristics of cavitation. As a result, the applicability of cavitation research has increased not only for theoretical analysis but also for practical engineering applications. Through theoretical and experimental analyses of the combined suppressive effects of fluid temperature, pressure difference, and turbulence intensity on hydrodynamic cavitation flow in Venturi-type reactors, variations in cavitation length and shape with respect to temperature have also been identified [29]. In addition, some studies have investigated the effects of cavitation dynamics and erosion patterns under submerged conditions on both flat and curved surfaces, thereby expanding the potential application of cavitation water jet technology to sustainable energy and cleaning processes [30]. Furthermore, the effect of nozzle rotation speed on the flow characteristics of water jets has been numerically analyzed, providing a theoretical basis for practical applications such as scale removal in industrial piping and wellbore cleaning in oilfields [31]. In addition, simulations of dual-nozzle cavitating water jets have been conducted to provide design guidelines for nozzles suitable for surface treatment of large structures [32], and the capability to simulate typical sheet-to-cloud cavitation flows around hydrofoils has also been evaluated, successfully reproducing the cavitation formation process [33]. In parallel, active research is also being conducted on cavitation phenomena occurring in the coolant flow around cylinder liners of internal combustion engines, reflecting the growing interest in understanding their impact on engine reliability and durability, as well as in identifying mechanisms to mitigate these effects. The correlation between pressure fluctuations and acceleration caused by the vibration of diesel engine cylinder liners and the concentration and intensity of cavitation has been investigated [34], the relationship between cylinder liner vibration and coolant pressure has also been analyzed to determine the cavitation risk associated with cylinder liner acceleration in medium-large-sized diesel engines [28]. It has also been demonstrated that vibration amplification of cylinder liners in internal combustion engines induces cavitation and erosion damage in the coolant, thereby providing a theoretical basis for mitigating damage caused by cavitation [35]. Meanwhile, according to the experimental study on cavitation erosion of cylinder liners by [PERSON] and [PERSON], the weight loss during cavitation erosion tests was found to be minimal in all coolant samples containing three different additives, confirming the effectiveness of these additives in preventing cavitation erosion [36]. Thus, coolant additives play a vital role in mitigating both corrosion and cavitation erosion of cylinder liners. Most previous studies on nitrite, a corrosion inhibitor, have been conducted separately, focusing either on corrosion or cavitation erosion. However, in field conditions, environments, where both corrosion and cavitation erosion occur simultaneously, can be present, potentially leading to severe cavitation erosion-corrosion problems. The objective of this study is to elucidate the effects of nitrite-based coolant additives on the corrosion and cavitation erosion behavior of cylinder liners in marine diesel engines. Electrochemical experiments and cavitation erosion tests were performed according to the presence or absence of additives and chlorides. Surface analyses after cavitation erosion tests were performed to investigate the mechanisms of corrosion and cavitation damage.