Thermal Treatment, Thermal Cycling, and Corrosion Evaluation of Palm Fatty Acids and Paraffin Wax as Phase Change Materials for Thermal Energy Storage Applications

Phase change materials (PCMs) are extensively explored for thermal energy storage (TES) applications. While paraffin wax is the most widely studied organic PCM, non‐paraffinic bio‐based fatty acids offer a more sustainable alternative. This study systematically evaluates seven palm fatty acids: caprylic, capric, lauric, myristic, palmitic, stearic, and oleic acids, focusing on thermal stability, reliability, and metal compatibility, compared with paraffin wax. In addition to standard thermal characterization, a heat absorption‐release test was performed to assess heat storage performance. PCM properties were analyzed before and after two thermal reliability assessments: thermal treatment (up to 700 h) and thermal cycling (up to 350 cycles). Differential scanning calorimetry (DSC) determined phase change temperature, latent heat, and specific heat capacity ( C p ), while thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) assessed thermal and chemical stability. The palm fatty acids exhibited slight variations in phase change temperature (0.03°C–3.6°C) and moderate melting latent heat reductions (−3.2% to −6.2% after thermal treatment, −7.5% to −13.8% after thermal cycling), comparable to paraffin wax (0.04°C–1.32°C, −7.0%, −10.3%, respectively). Similar to paraffin wax, changes in C p , heat storage performance, TGA, and FTIR results further confirmed the thermal reliability of palm fatty acids. Twelve‐week corrosion tests showed decreasing corrosion rates with time and confirmed the compatibility of all tested PCMs with stainless steel, aluminum, copper, and brass, with most corrosion rates remaining below the critical threshold for long‐term use. Overall, palm fatty acids demonstrate high thermal reliability, stability, and metal compatibility comparable to paraffin wax, establishing them as sustainable bio‐based PCMs for long‐term TES applications.