Oxidation of a metal is a chemical reaction between oxygen in the air (dry oxidation) or in an aqueous medium (wet oxidation) and the surface of this metal, generally resulting in a change in appearance.
Oxidation of iron :
There are three degrees of iron oxidation :
FeO: Ferrous oxide or calamine, black or dark grey in appearance.Bound to the metal, it is poorly soluble in hydrochloric acid,
Fe3O4: Black-looking magnetic oxide or magnetite.Soluble in hydrochloric acid,
Fe203: Ferric oxide or hematite, commonly called rust, reddish yellow in appearance.Soluble in hydrochloric acid.
These 3 oxides are in order from the metal: Fe – Fe0 – Fe3O4 – Fe203.
Oxidation of copper :
Copper and its alloys are covered with oxides of different types:
CuS04, 3Cu(OH)2: Copper sulphate called grey green,
CuO: Black-looking cupric oxide,
Cu2O: Red-looking cuprous oxide.
Oxidation of zinc :
Oxides usually form on zinc-treated parts by hot dip galvanizing.
Parts treated by electrolytic zinc plating are passivated (iridescent-looking treatment) allowing protection against oxidation.
ZnO: Zinc oxide created in dry atmosphere.
ZnCO3, 2Zn(0H)2,H2O: Zinc oxide or white rust, formed in a wet environment.
Oxidation of aluminum :
Aluminum is coated with a layer of transparent oxide, naturally formed, Al203, called alumina.
Descaling operation :
Alkaline descaling is mainly used to eliminate oxides generated when burning grease and oils (parts of thermal engines) or hot chemical reactions in moulding (moulds for plastic parts, rubber, aluminium, zamak, etc.).
The descaling operation allows the renovation of mechanical parts without altering the metallographic quality of the metal and the dimensions of the part and is generally carried out in a strongly alkaline medium and at high temperature.
Below are our standard BONDERITE® DESCALING products :
BONDERITE C-AK 4181 L
BONDERITE C-AK 664 D
BONDERITE C-AK STL
List not exhaustive, contact us for a recommendation or if you are looking for another reference.