Thursday, 8 May 2014

Iron produces a spectrum of colour

Elizabeth Henderson
Product Development Manager

This month’s blog discusses an element used by Itac only as a compound – iron. But as the mainstay of the construction industry and one of the commonest elements of our planet, it plays a major role in our business. We use coloured iron compounds in our products - iron’s oxides are familiar as rust, and they are refined to produce stable pigments of either red or yellow colour. They have excellent resistance to sunlight as well as good chemical stability. With good hiding power and colour strength they make a valuable contribution to the appearance of a painted item.
 In addition to its place in the red and yellow part of the spectrum, iron is the key component of Prussian Blue pigment, which is iron(III) ferrocyanide. The yellow colour of FeO arises from iron in oxidation state 2, the red in Fe2O3 from iron in oxidation state 3. The characteristic blue of iron(III) ferrocyanide arises from the presence of iron in both oxidation states in the compound.  These three colours all from the same element are demonstrated in the colours found in natural mineral Tiger’s Eye. This material has a characteristic fibrous appearance associated with its source crocidolite which has been replaced by silica, and the three naturally occurring colours (yellow-brown, red and blue) arise because of contamination by iron in various oxidation states.
Itac has recently bought Delvemade Ltd, and we now supply paints for roofing, designed to prevent iron doing what it likes to do most of all – oxidise to rust. ‘Delcote’ coatings are applied to corrugated iron which has been factory finished in a coil-coating process but needs refreshing because of weathering and exposure to pollutants. The paint has to bond successfully to the original finish and extend the life expectancy of the building as well as improving its appearance.
The magnetic properties of iron are also exploited in specialised adhesives and coatings. Magnetite (mixed oxidation-state iron oxide) is incorporated in specialist inks (seen on the bottom of cheques) which can be read by magnetic readers. High-spec adhesives have been devised incorporating very fine iron dust, which heats up very quickly in a magnetic field and initiates the thermal cure of the adhesive medium very quickly.

No comments:

Post a Comment