Preparation of aluminide coatings on the inner surface of tubes by heat treatment of Al coatings electrodeposited from an ionic liquid

• Al coating is prepared on the inner surface of one-meter tube.
• Al coating shows good adherence to the substrate.
• The thickness of Al coating is uniform along the tube.
• Aluminide coating is obtained by heat treating Al coating.
• Structure of aluminide coating is regulated by different thickness of Al coating.

Aluminide coatings were prepared on the inner surface of 316L stainless steel tubes with size of Ø 12 mm × 1000 mm by heat-treating Al coatings electrodeposited from AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3–EMIC) ionic liquid at room temperature. Studies on the electrolytic etching pretreatment of stainless tubes before Al coating electrodeposition were carried out. The Al coating showed good adherence to the substrate after electrolytic etching at 10 mA/cm2 for 10 min. The thickness of Al coatings was uniform along the tube. The structure of prepared aluminide coatings can be regulated by different thickness of Al coating. The outer layer of aluminide coatings was FeAl, Fe2Al5 and FeAl3 for the samples of 1-μm, 5-μm and 10-μm thick Al coatings, respectively.