Simple spray method preparation of slow-release porous microcapsule for long-term active anti-corrosion and scale-inhibiting coatings

Anti-scaling is a key challenge in various industrial productions. The use of coatings is the most effective strategy for protecting metal equipment. An excellent scale inhibitor is 1-hydroxy ethylidene-1, 1-diphosphate (etidronic acid) (HEDP), which is usually incorporated into wastewater and discharged directly with the water flow. In this study, HEDP was coated with poly-α-ethyl cyanoacrylate (PEC) by a simple spray method. The corresponding slow-release microcapsules, which we named PEC&HEDP, were successfully prepared. In addition, a correct mass of the microcapsules was added to the spray polyurea elastomer (SPUA) coating. The resulting SPUA/PEC&HEDP70&30 composite coating exhibited excellent anti-corrosion and scale-inhibiting effects. Electrochemical impedance spectroscopy and salt spray corrosion test were used to assess the corrosion resistance of the coating. The results showed that the barrier performance of the composite coating improved significantly. In addition, the scale inhibition performance of the composite coating was tested in a supersaturated CaCO3 solution. The results showed that the scale inhibition rate of the composite coating was higher by as much as 80.5% relative to the pure SPUA coating. This work provides a new and simple method for designing and preparing a slow-release microcapsule composite coating intended for scale control.