In Situ Polymerized Self-Healing Microcapsules as Multifunctional Fillers toward Phosphate Ceramic Coatings

The
protective efficacy of chemically bonded phosphate ceramic
coatings (CBPC) is notably diminished owing to the presence of micropores
and inadequate self-healing capacity in prolonged corrosive environments.
Consequently, it is imperative to augment the corrosion and wear resistance
of phosphate ceramic coatings while imbuing them with self-healing
capabilities. In this work, a novel self-healing phosphate ceramic
coating (MC-PTx@CBPC, x = 0.5, 1.0, 1.5) is designed by urea-formaldehyde (UF) in situ polymerization
of nanoscale microcapsules encapsulated with 1H,1H,2H,2H-perfluoro­decyltriethoxysilane
(PFDTES) and evaluated in detail for corrosion and wear resistance.
The corrosion inhibition efficiencies of all formulated MC-PTx@CBPC (x = 0.5, 1.0, 1.5)
coatings exceed 90%, with the impedance modulus at the lowest frequency
(|Z|f=0.01) showing enhancements
of 1–2 orders of magnitude compared to pure CBPC. Moreover,
the self-healing function becomes active during prolonged immersion.
This can be primarily ascribed to the formation of a unique micronanostructure
facilitated by nanoscale microcapsules and micrometer-sized alumina
ceramics, bonded via the AlPO4 phase. This structure enhances
both the hydrophobicity and the bonding strength of the coating. Specifically,
following prolonged immersion, the encapsulated PFDTES is liberated
from the microcapsules, undergoing hydrolysis and subsequent polymerization
upon contact with the electrolyte to form a protective thin film.
This film efficiently obstructs the ingress of corrosive agents. Furthermore,
the special micronanostructure enhances the hardness of the coating
and the releasing PFDTES can form a lubricating film at the interface
of abrasion, thus reducing the wear rate and friction coefficient
of the MC-PTx@CBPC (x = 0.5, 1.0, 1.5). Therefore, MC-PTx@CBPC
(x = 0.5, 1.0, 1.5) possesses excellent corrosion
protection, tribological properties, and self-healing capabilities,
which provide thought-provoking ideas for phosphate ceramic coatings
to protect metals in harsh environments.