Phase change materials (PCMs) are commonly applied in thermal energy storage (TES) units. They offer an outstanding possibility of temporary accumulation of energy delivered to the system (from waste or renewable sources e.g. solar) in the form of latent heat of fusion, which is further recovered during solidification stage and can be used to facilitate various technological processes. Among widely utilized phase change materials different salts and their mixtures or solutions can be distinguished such as hydrates or eutectic composition of nitrates. Their main drawback is that they exhibit low thermal conductivity what drastically prolongs their heating period up to the full melting, making them unsuitable to be charged directly from solar thermal collectors at some latitudes. One way to mitigate this inconvenience is to immerse thin-walled metallic structures within PCM deposits to increase the effective heat transfer rate. Such thermal enhancers can be fabricated by a combination of two novel technologies: 3D printing (fused deposition modelling, FDM) and subsequent investment casting. For this purpose cellular honeycomb-type structures can be designed and cast from selected aluminum alloys (e.g. EN AC-44200). Presence of these lightweight castings in LTES units can not only speed up the charging process but also help to homogenize the overall temperature distribution. Another key aspect of this solution is related to the corrosion risk of metal parts in harsh environment of molten salts, especially in relation to salt hydrates (e.g. magnesium chloride salt hydrate MgCl2·H2O). A protective measure may be to deposit anti-corrosive coatings done by plasma electrolytic oxidation (PEO) method on the surface of cast aluminum inserts.