Baroutian, SaeidZhang, Anqi (Angie)2025-01-072025-01-072024https://hdl.handle.net/2292/70926This research investigates the corrosion behaviour of stainless steel AISI 304 in evaporation condensate reclamation systems within a New Zealand local dairy plant, providing insights into a critical issue in the broader dairy industry. The study addresses a gap in existing research on the sustainable reuse of evaporation condensate, with previous investigations rarely examining the corrosive impact on stainless steel 304 infrastructure. Notably, only one prior published study investigated potential corrosion caused by low levels of dissolved solids and acidity in dairy evaporation condensate. However, it lacked experimental data and did not specify the affected metals. The experimental approach involved simulating various factors that promote corrosion to assess potential industry corrosion rates. Electrochemical testing and surface studies were utilised to explore corrosion mechanisms. Results discovered that solutions containing 0.5 mg/L chlorine exhibited the highest corrosion rate at 0.00996±0.0000232 mm/year at room temperature. Evaporation condensate lite and simulated evaporation condensate with milk additions showed corrosion rates of 0.00622±0.000371 mm/year and 0.00517±0.00172 mm/year, respectively, while deionised waters used to simulate treated evaporation condensate recorded rates of 0.00765±0.00018 and 0.00705±0.0000301 mm/year. Factors such as low ion concentration, acidity and high levels of dissolved gases were identified as corrosion initiators. The corrosion rate of all water samples increased with rising temperature. Optical and scanning electron microscopy (SEM) results observed that chlorine solutions created more giant pits during long-term immersion, and simulated evaporation condensate showed the most pits. Energy-dispersive spectroscopy (EDS) supported the idea that chlorine and microbial activity contribute to corrosion issues primarily in the long term. These findings implied that the operational conditions in dairy water reclamation systems affect the longevity and reliability of stainless steel 304 components. Recommendations included introducing inhibitors to increase pH and reduce acidity, optimising water treatment to manage chlorine and oxygen levels, upgrading to more corrosion-resistant materials, and enforcing regular maintenance protocols. This study filled a knowledge gap concerning stainless steel degradation in water reclamation systems in the dairy industry. It offered significant insights to enhance the durability of equipment and infrastructure used and, hence, the efficiency of dairy processing.https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmThesisCopyright: the author