Calcium phosphate deposition from simulated milk ultrafiltrate on different stainless steel-based surfaces

In order to reduce the fouling caused by milk during heat treatment, it is important to know more about the precipitation process of calcium phosphate, the main mineral component of milk deposits. This work was mainly focused on the relationship between calcium phosphate fouling behaviour and the surface properties of the materials used as metallic substrata. The foulant solution used in this work was an aqueous solution that simulates the mineral composition of milk and the deposition of calcium phosphate was studied on several stainless steel-based surfaces with different surface energy properties, obtained by ion implantation (SiF3+ and MoS2), coating by plasma chemical vapor deposition (SiOx) or autocatalytic coating (Ni-P-PTFE). The experiments were performed in a batch system, using a rotating disk apparatus. The calcium phosphate deposits formed were characterized according to the rate of formation, thickness and resistance to removal under increasing shear stresses. Based on the data presented in this work, it could be concluded that fouling caused by calcium phosphate is affected by the surface energy properties of the metal substrata since different surfaces develop different deposit structures which have, consequently, different resistance to removal.