As we move on to analyzing all the metal objects we’ve found at Riverside, our preliminary rust-removal attempts have filled our lab in Brooklyn with an “interesting” aroma and quite a lot of fizzing noises. We feel a bit like mad scientists!
Most metals corrode during burial, forming thick layers of crust. This is why metals often require the most cleaning. Corrosion on iron usually takes the form of rust, a generic term for the minerals that form when metallic iron reacts with oxygen and water vapour, creating a crust that can be shades of brown, reddish-brown, yellow, or orange. The corrosion itself can give us clues as to the metal’s composition and the chemistry of the soil, but it obviously also obscures the details of the object. The key is to find the best way to eliminate corrosion while at the same time keeping the object and its diagnostic features intact!