Solvothermal Synthesis of Acmite Conversion Coatings on Steel

Abstract

Acmite (NaFeSi 2 O 6 ) films were formed on steel coupons via solvothermal reaction of silica, sodium hydroxide, and 1, 4-butanediol in an autoclave under autogenous pressure. Systematic variation in processing variables led to homogenous coatings comprised of pinacoidal acmite grains with an average grain size of~33 lm. The coatings were produced on the steel coupons from reactant conditions of 0.635 m SiO 2 , 2.546 m NaOH, and 3.087 m 1,4-butanediol for 72 h at 240°C.

Magnetite thin film on mild steel formed by hydrothermal electrolysis for corrosion prevention

“…Rihan and Nesic [36] explained that under hydrothermal alkaline solutions, the most often related to formation of a protective film on the mild steel surface is magnetite film, although there are a few proposals suggesting different mechanisms for this process. Whalen et al [22] also reported conversion of steel surfaces to magnetite in highly alkaline oxidizing baths containing NaOH at 240°C with autogenous pressure. They explained that the initial surface of steel was converted into magnetite and then after additional reaction time (72 h), only acmite was apparent at the surface of steel.…”

“…Several literatures have reported that hydrothermal method has been becoming one of the most important wet-chemical routes for synthesizing nanostructured materials [19][20][21][22][23][24][25][26]. Hydrothermal method is based on the use of water as solvent at temperatures between 100 and 374°C and under pressure high enough to maintain the liquid state and lead to increase the solubility of a solid and to speed up reactions between solids.…”

“…They have successfully formed the octadecahedron morphology that was rare but they still didn't study about the effect of temperature and pressure to the formation of the magnetite film. Recently, Whalen et al [22] showed a simple practical approach for the formation of acmite (NaFeSi 2 O 6 ) coatings with a uniform, passivating coverage on steel at substantially mild reaction conditions. Acmite films were formed on steel via solvothermal reaction of silica, sodium hydroxide, and 1,4-butanediol in an autoclave under autogenous pressure at 240°C.…”