Wettability of Metal Surfaces Affected by Paint Layer Covering

The aim of the work was to quantify the surface wettability of metallic (Fe, Al, Cu, brass) surfaces covered with sprayed paints. Wettability was determined using the contact angle hysteresis approach, where dynamic contact angles (advancing Theta (A) and receding Theta(R)) were identified with the inclined plate method. The equilibrium, Theta(Y), contact angle hysteresis, CAH = Theta (A) - Theta(R), film pressure, P, surface free energy, gamma SV, works of adhesion, WA, and spreading, WS, were considered. Hydrophobic water/solid interactions were exhibited for the treated surfaces with the dispersive term contribution to gamma SV equal to (0.66-0.69). The registered 3D surface roughness profiles allowed the surface roughness and surface heterogeneity effect on wettability to be discussed. The clean metallic surfaces turned out to be of a hydrophilic nature (Theta (Y) < 90 degrees) with high gamma SV, heterogeneous, and rough with a large CAH. The surface covering demonstrated the parameters' evolution, Theta(A)up arrow, Theta(R)up arrow, gamma SV down arrow, WA down arrow, and WS down arrow, corresponding to the surface hydrophobization and exhibiting base substratumspecific signatures. The dimensionless roughness fluctuation coefficient, eta, was linearly correlated to CAH. The CAH methodology based on the three measurable quantities, QA, QR, and liquid surface tension, gamma LV, can be a useful tool in surface-mediated process studies, such as lubrication, liquid coating, and thermoflow.

Automated summary

The aim of this study was to quantify the surface wettability of metallic surfaces covered with sprayed paints. The results showed that the treated surfaces exhibited hydrophobic water/solid interactions and the surface roughness and heterogeneity affected the wettability. The findings are important for surface-mediated process studies such as lubrication, liquid coating, and thermoflow.