The necessity of measuring the thickness of Bridges’ Scale Armour Paint

Micaceous iron oxide (MIO) coatings or ‘scale armour paint’ are to be found wherever maximum corrosion protection is essential – steel bridges, power poles and even famous structures like the Eiffel Tower or Sydney Harbour Bridge. All of these structures are protected against the elements with a layer of this specific type of paint and in order for it to last as long as foreseen by the manufacturer; a certain layer of thickness must be applied and checked. Micaceous iron oxide is not ground iron, it’s rather more a form of the naturally occurring mineral hematite, mixed as an additive into paint. MIO forms an additional, protective barrier against corrosion. A crystalline iron oxide mineral consisting mainly of iron III oxide, powdered MIO is flaky in texture and when suspended in viscous epoxides, the minerals align themselves parallel to the surface as the paint dries forming a dense, nearly impenetrable shield of overlapping plates that repels water and other rust forming elements. Therefore referred to as ‘scale armour paint’, MIO coatings are used for extremely heavy duty applications. A red-brown tint is typical for MIO paint and famous structures such as the Eiffel Tower in Paris, the Giant Ferris Wheel in Vienna, the Sydney Harbour Bridge and Istanbul’s Bosphorus Bridge are all characterised and protected by it. While found primarily on galvanised steel parts, MIO coatings can also be used on non-galvanised steel, iron and aluminium. However, the reliability and longevity of the corrosion resistance depend on the thickness of the coatings, which are generally applied about 80-120 microns thick. Just like normal paint layers, the thickness of MIO coatings can be measured using the magnetic induction method, as hermatite itself is antiferro-magnetic, therefore the IO coatings are usually not magnetic either. Instruments from Fischer’s handheld FMP series are ideally suited for this task. Due to the paints relatively high surface roughness, Fischer also recommends the use of one of its robust probes with carbide metal tips, which have particularly long service life, the F20H. The addition of platelet shaped minerals to so called MIO coatings boosts the corrosion protection for structures that are constantly exposed to the weather. Using the handheld instruments from the FMP series and the durable F20H probe, the thickness of MIO coatings can be measured quickly and accurately. Visit www.fischergb.co.uk for more information on corrosion protection and the FMP series

For more information on The necessity of measuring the thickness of Bridges’ Scale Armour Paint talk to Fischer Instrumentation