**5. Conclusions**

The fabrication method of a novel composite metal UniPore structure with longitudinal pores was investigated in this study. For the first time, the surfaces of the longitudinal copper cellular structure were covered by a second metal, a thin layer of corrosion resistant stainless steel. Two assembly arrangements of the copper UniPore structure with stainless steel pipes layered at the inner surface of the inner copper pipes were successfully fabricated. Microstructure analysis of the fabricated samples demonstrated good interface bonding between the component walls as well as providing efficient and mechanical properties in the case of structural applications. The authors believe that the proposed composite UniPore structures have corrosion resistance, high temperature resistance, and high e fficiency when used as heat exchangers or heat sinks, which will be proven in further study.

**Author Contributions:** Conceptualization, K.H.; Methodology, K.H.; Validation, M.N., S.T., and M.V.; Investigation, M.N. and M.V.; Resources, S.T.; Data evaluation, M.N. and S.T.; Writing—original draft preparation, M.N.; Writing—review and editing, M.V., Z.R., and K.H.; Supervision, Z.R. and K.H.; Project administration, Z.R. and K.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors acknowledge the financial support from the Slovenian Research Agency—ARRS (research core funding No. P2-0063).

**Conflicts of Interest:** There are no conflicts of interest.
