Several ancient world heritage iron-based structures present quite good corrosion resistance that is generally related to the presence of phosphorus in their metallic substrate. However, the exact protection mechanisms have not yet been explained. In order to better understand the role of this element, in the conditions of atmospheric corrosion, both its distribution and speciation were investigated. To do so, a combination of microXRF and microXANES at the P K-edge was used, together with micro-Raman investigations. This methodology was applied on two types of ancient ferrous samples. For both types, two sources of phosphorus, global endogenous as well as localised exogenous were revealed. From these two sources, the phosphorus was seen to be heterogeneously distributed in the corrosion products. The shape of the XANES spectra demonstrated that the phosphorus is present as phosphate complexes with all the iron corrosion products present in the layers.

Intermetallic compounds are key materials for energy transition as they form reversible hydrides that can be used for solid state hydrogen storage or as anodes in batteries. AB_y compounds (A = Rare Earth (RE); B = transition metal; 2 < y < 5) are good candidates to fulfill the required properties for practical applications. They can be described as stacking of [AB₅] and [AB₂] sub-units along the c crystallographic axis. The latter sub-unit brings a larger capacity, while the former one provides a better cycling stability. However, AB_y binaries do not show good enough properties for applications. Upon hydrogenation, they exhibit multiplateau behavior and poor reversibility, attributed to H-induced amorphization. These drawbacks can be overcome by chemical substitutions on the A and/or the B sites leading to stabilized reversible hydrides. The present work focuses on the pseudo-binary Sm₂Mn_xNi_7−x system (0 ≤ x < 0.5). The structural, thermodynamic and corrosion properties are analyzed and interpreted by means of X-ray diffraction, chemical analysis, scanning electron microscopy, thermogravimetric analysis and magnetic measurements. Unexpected cell parameter variations are reported and interpreted regarding possible formation of structural defects and uneven Mn distribution within the Ni sublattice. Reversible capacity is improved for x > 0.3 leading to larger and flatter isotherm curves, allowing for reversible capacity >1.4 wt %. Regarding corrosion, the binary compound corrodes in alkaline medium to form rare earth hydroxide and nanoporous nickel. As for the Mn-substituted compounds, a new corrosion product is formed in addition to those above mentioned, as manganese initiates a sacrificial anode mechanism taking place at the early corrosion stage.