In SK she has several sets of teeth, but the metal one "was made out of some kind of silvery metal, shining like a sword", so it wasnt specified as Iron. The shears are described as "rusty shears", though since it's not "rust-colored" it remains possible that the oxidation was non-specific; silver can be rusty but it's black, or green for copper-based alloys. Many of my old "rusty" tools appear to have black rust, rather than the stereotype red-rust of iron.
But a WOJ makes a strong implication that those shears are the mythic shears of Atropos, used to Cut the strings of Fate and end lives; I tend to question whether such a cosmically significant artifact would be made of common materials.
Not necessarily relevant to the story, but the post....
Red Rust
Hydrated oxide Fe2O3•H2O
(high oxygen/water exposure)
Rust from Iron (III) oxides forms due to high oxygen and water exposure resulting in red rust.
•Red rust is the result of heavy exposure to air and moisture, combined many times with a contaminate (salt).
•This type of rust is most likely atmospheric because typically there are no signs of rust runs or streaks on the metal parts/equipment where the rust has formed.
•With red rust, there is uniform corrosion, most often from a very corrosive environment.
Yellow Rust
Iron oxide-hydroxide FeO(OH)H2O
(high moisture)
Rust from Iron (III) oxides that is a very soluble iron oxide results in yellow rust.
•Yellow rust is distinguishable in recessed areas of the metal parts/equipment where the rust “runs and drips” (solvated rust).
•Yellow rust forms as a result of very high moisture content. It frequently found in settings where puddled/standing water has most likely been present.
Brown Rust
Oxide Fe2O3
(high oxygen/low moisture)
Rust from Iron (III) oxides with high oxygen and low moisture results in brown rust.
•Brown rust is a drier rust than those mentioned above.
•It is most likely atmospheric – having formed as a result of water and oxygen in the atmosphere and presenting as a reddish-brown crust on the metal’s surface.
•Brown rust is sometimes localized rust which appears as non-uniform spots or only in certain areas rather than over the whole surface. It can be the result of a contaminate on the metal’s surface often originating from the manufacturing process.
Black Rust
Iron (II)oxide – Fe3O4
(limited oxygen)
Rust from Iron (III) oxides with limited oxygen and low moisture results in black rust.
•Black rust can be visually identified as a thin, black film which is the result of oxidation in a low oxygen environment.
•Black rust has an appearance of almost a black stain. Most likely the areas exhibiting the black rust had something covering them, which prevented oxygen from reaching the surface.
•This type of rust is a more stable rust layer that does not propagate as rapidly as other rust forms.
