Anticorrosive pigment for smart and green protective coatings: An alkyd resin coating incorporating lanthanum-loaded hydroxyapatite, derived from a phosphate mining industry by-product

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Vol. 35; no. 11; p. 104666
• Main Authors: Elmourabit, Mohammad, Zarki, Youssef, Arfoy, Brahim, Allaoui, Ibrahim, AitAghzzaf, Ahmed, Azzouz, Abdelmonaim, Bouchta, Dounia, Chaouket, Faiza, Draoui, Khalid
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: Alkyd coating; EIS; Lanthanum-loaded hydroxyapatite; Phosphate sludge; Smart corrosion inhibition; Smart corrosion inhibition; Lanthanum-loaded hydroxyapatite; Phosphate sludge; Alkyd coating; EIS
• ISSN: 0921-8831
• DOI: 10.1016/j.apt.2024.104666

[Display omitted] •Eco-friendly La-HAp derived phosphate sludge was developed.•Achieves 82% corrosion inhibition efficiency via dual anodic and cathodic mechanisms.•Protective layers of lanthanum hydroxide and iron orthophosphates enhance durability.•Smart coatings with synergistic barrier, ion release, and trapping effects.•Innovative use of waste materials for superior corrosion protection performance. Intelligent anti-corrosive coatings have gained considerable interest as a method to protect metals. This approach offers an effective strategy for mitigating corrosion by providing advanced control over the process. In this research, lanthanum-loaded hydroxyapatite pigment (La-HAp) was successfully synthesized using phosphate sludge (PS) waste. The pigment was incorporated into an alkyd resin coating to provide smart corrosion protection for mild steel exposed to a saline solution. The synthesized pigments were characterized using various analytical techniques, including FTIR, XRD, and SEM−EDS. The inhibitory performance of La-HAp on mild steel submerged in a 3% NaCl solution was evaluated using linear polarization and EIS techniques. The findings demonstrated substantial inhibitory effectiveness, achieving 82% inhibition efficiency. Further investigation compared the protective capabilities of modified (C-La-HAp) and reference (C-Ref) alkyd coatings on carbon steel using EIS. The results indicated significant corrosion protection enhancement with 5% La-HAp, showing a polarization resistance of 19.7 MΩ·cm2 after four weeks of immersion in the aggressive solution. This corrosion resistance is primarily attributed to the formation of a barrier against the corrosive environment and the trapping of Cl- ions by the HAp, accompanied by the release of La, phosphate, and calcium ions. La ions react with OH- ions produced in the cathodic zones to form a uniform protective layer of Lahydroxides, while iron orthophosphates provide additional protection at anodic sites. This synergistic blend of mechanisms imparts intelligent corrosion-inhibiting properties to the alkyd resin, effectively guarding against the damaging effects of corrosive agents.