Fig. 1

Macro-pictures of bare brass at t = 0 (a.1) vs t = 1, where its yellowing can be appreciated (a.2). EIS measurement mark on Owatrol at t = 1 on steel (b.1) and on brass (b.2). Defects on the coatings of B72/TiO₂ on steel before ageing (c). Macro + zoom of C80 on steel at t = 1 showing the rough surface due to the presence of wax flakes (d). The rest of the coatings (e.1) PHS/PEOX, (e.2) INC and (e.3) B72, are apparently unchanged at t = 1; only a general yellowing of the metal is visible, as is the uncoated brass