In the framework of the protection of copper objects exposed to atmospheric corrosion, different solutions are envisaged, among them carboxylate treatments (HC₁₀). In this study, an analytical approach based on complementary techniques from micrometer to nanometer scale (μRS, SEM-EDS, SAM) is used to describe the properties of the corrosion products layer (CPL) and determine the penetration depth of the HC₁₀ protection treatment inside the CPL of copper samples issued from the roof of the Saint Martin church in Metz. The CPL consists in a thick brochantite layer (20 to 50 μm), mainly composed of Cu₄SO₄(OH)₆, on top of a thinner (1 to 5 μm thick) cuprite layer, Cu₂O, acting as a natural corrosion barrier on the metal. Application of the organic treatment is implemented by immersing the corroded samples in HC₁₀ solution, consistent with future requirements for large scale applications. Even for short-term duration (one minute), the HC₁₀ treatment penetrates to the cuprite/brochantite interface, but Cu(C₁₀)₂ precipitate is only detected locally, whereas for a longer immersion of thirty minutes, it is present in higher proportions in the whole brochantite layer, filling the pores, up to the cuprite/brochantite interface. Cu(C₁₀)₂ acts as a second inner barrier and prevents liquid infiltration.

Matériaux & Techniques, la revue des matériaux industriels et de leurs techniques de mise en oeuvre

The evolution of the passivating layer (during the first reduction/reoxidation cycle, in function of the number of reduction/reoxidation cycles and with the storage of the electrode in the electrolyte) formed at the surface of a lithiated carbon electrode in LiCF3SO3/carbonates mixture electrolyte has been followed by using 1 MeV 4He+ induced Rutherford Backscattering Spectrometry (RBS). Two RBS simulation codes "RUMP" and "PERM" , whose approaches are different, have been applied to the treatment of the RBS data and have allowed to obtain informations about the structure (thickness and atomic elemental composition) of the passivating layer. These two codes provide similar results. The passivating layer has a thickness in the range 20-30 nm. Its structure appears to be complex with the presence of two different sublayers respectively composed of the reduction products of the salt in the inner sublayer (with the main presence of fluorine and sulphur indicating the possible existence of LiF and Li2S) and reduction products of the solvents in the outer sublayer (with a high concentration in oxygen indicating the presence of Li2CO3 and RCO3Li where R is an alkyl radical).