Corrosion protection of steel bar enabled by monofluorophosphate-bearing composites with sustained-release capability

This paper selected the polyethylene (PE) and polystyrene (PS) as polymer carriers of the sodium monofluorophosphate (MFP) to prepare PE/MFP and PS/MFP composites using melt-extrusion technique with a sustained-release capacity for smart corrosion protection. The releasing behavior of two MFP-containing composites in the simulated concrete pore solution was evaluated in terms of residual content, releasing rate and the side/fractured surface micro-morphologies. Besides, related releasing mechanisms of MFP-bearing polymer composites are explained, which are different from the mechanisms of most microcapsules and tablets. The experimental analyses showed that two composites all displayed a uniform elemental distribution on their side surface and intrinsic hydrophobicity. The PE/MFP composites obtained higher initial encapsulation efficiency and a lower but relatively controllable releasing rate compared to the PS/MFP composites due probably to the higher hydrophobicity and crystallinity of the PE carrier. In addition, the physical appearance of the corroded carbon steel bar after immersion in sodium chloride-contaminated simulated concrete pore solutions and corresponding electrochemical outcomes revealed that PE/MFP composites generally led to better corrosion protection performance than the PS/MFP counterpart, which could be due to their better sustained-release capacity. The obtained composites provide another promising option as concrete inhibitors, making inroads into improving the long-term durability of concrete structures.