Tuning the mechanical integrity and corrosion performance of open-cell copper foams: identification of an optimization threshold

Abstract

In this work, Porous copper foam samples were fabricated by a space-holder technique with water-atomized copper powder and sodium chloride (NaCl) particles in weight fractions ranging from 10 to 35 wt%. The powders were mechanically mixed at a 10:1 ball-to-powder ratio and 150 rpm for 2 h. The effects of space-holder content on the physical, mechanical, tribological, and electrochemical performance were systematically investigated. Increasing the NaCl fraction precisely controlled the total porosity, from 39.15% to 57.76%, and reduced the bulk density from 5.452 to 3.785 g/cm³. XRD and SEM analyses confirmed a single-phase FCC copper matrix and a structural transition from isolated pores to a highly interconnected open-cell network. Consequently, Vickers hardness, compressive yield strength, energy absorption capacity decreased from 52.12 to 29.23 HV, 18.25 to 1.65 MPa, and 35.73 to 10.46 MJ/m³, respectively, following a modified Gibson–Ashby model (R2 = 0.95). Concurrently, the coefficient of friction and specific wear rate increased (reaching a maximum of 0.73 mm³/N·m under 15 N for 35 wt% NaCl) due to strut thinning and localized delamination. Electrochemical evaluation in 3.5 wt% NaCl solution revealed an optimization threshold for sample fabricated with 25 wt% NaCl, which exhibited the lowest corrosion rate of 0.918 mm/y, and the highest polarization resistance (Rp) of 267.28 Ω, due to a stable Cu2O passive film. Exceeding this threshold at 30 and 35 wt% NaCl led to structural instability and stagnant electrolyte zones, accelerating corrosion kinetics. Overall, lower-porosity porous copper foam architectures offer superior structural energy absorption, whereas the 25 wt% NaCl configuration achieves an optimal balance between mechanical integrity and corrosion resistance.