Fly ash applied as Combined Extender Pigment and Carrier of Inhibitor-loaded LDH

Fly ash (FA) was used successfully as a carrier for the corrosion inhibitor molybdate and applied as an extender pigment in an epoxy coating. To enhance interaction, molybdate was attached to FA through intercalation in layered double hydroxide (LDH), facilitated by surface modification of FA. Molybdate was incorporated into LDH either via direct synthesis or ion exchange. Directly synthesized LDH significantly increased molybdate storage in FA. The FA-inhibitor combination was tested in three ways: molybdate release kinetics, corrosion of an ultra-low carbono (ULC) steel in chloride solution, protection of ULC steel conferred by particles embedded in an epoxy coating. Short-term molybdate release was favored by ion exchange, long-term release by deglomeration of LDH. ULC steel corrosion inhibition in 0.1 M NaCl reached 89%. Incorporating the material into epoxy coatings mitigated steel corrosion, validated by electrochemical impedance spectroscopy. This study underscores the efficacy of FA-LDH-molybdate systems in corrosion protection.

Keywords:
Fly ash; LDH; molybdate; inhibitor carrier; coating; corrosion