SOFT CHEMICAL STRIPPING OF ALUMINIDE COATINGS AND OXIDE PRODUCTS ON NI SUPERALLOYS

S. Poupard (1) , J.F Martinez (1) , Fernando Pedraza (1)

1 LEMMA - Laboratoire d'Etude des Matériaux en Milieux Agressifs

Turbine components are submitted to very aggressive environments and particularly to high temperature corrosion and /or oxidation. Because of their high cost, they have to be repaired instead of being replaced. Prior to refurbishment and recoating, the components have to be fully stripped to remove the oxide products and defective coatings. In this work, various soft chemical stripping methods are studied based on pitting acids and agents as well as oxidising acids in organic and aqueous media. The effect of the immersion time is also investigated. The feasibility of the dissolution reactions has been evaluated through thermodynamic calculations. It will be shown that the most effective baths are those containing relatively high concentrations of pitting reagents in organic media. Aqueous solutions lead to pitting of the superalloy. The stripping mechanisms have been discussed in terms of the dissolution of coating grain boundaries once the solution has passed through the oxide scales.

Mots clés: soft chemical stripping; aluminide coating; oxide scales; Ni-base superalloy

Domaines: Ecotoxicologie; Matériaux

S. Poupard, J.F Martinez, Fernando Pedraza. SOFT CHEMICAL STRIPPING OF ALUMINIDE COATINGS AND OXIDE PRODUCTS ON NI SUPERALLOYS. Surface and Coatings Technology, 2008, 202, pp.3100-3108. ⟨10.1016/j.surfcoat.2007.11.013⟩. ⟨hal-00512240⟩