is why such coatings perform poorly in comparison to some lamellar glass fl akes. One of
the many reasons coatings
manufacturers formulate coatings using glass fl ake is to increase the mean path distance of ion migration through the coating. T e higher the aspect ratio of the glass fl ake, the greater the ion migration distance becomes. T us it is clear that an optimum level of high aspect ratio glass fl ake is required to aff ord ultimate anti-corrosion levels of performance. At too low a level, the anti-corrosion properties will be diminished and at too high a level the coating may become brittle.
Gauging performance When selecting a glass fl ake epoxy coating, some people turn to Norsok M-501 Ed. 6 for guidance. System 7A uses a set of prequalifi ed tests specifi cally for splash zone areas. What confuses many, however, is that Norsok M-501 does not offer a coatings lifetime performance guarantee; it merely provides
Low aspect ratio glass particles
High aspect ratio glass pigment
Ion migration through different aspect ratio glass pigments; the higher aspect ratio offers greater barrier protection
SUBSTRATE
a performance standard. T us, whilst glass fl ake epoxy coatings may pass this standard, a coatings specifi er is none the wiser as to the coating’s projected lifetime in an off shore environment. This is why supporting in-service performance is so critical in the coatings selection process. A recent survey of the now decomissioned Hutton TLP has
shown outstanding in-service performance aſt er almost 30 years off shore. OMT
Reference 1. NACE Paper 09009 – 2009 “Heavy duty glass flake coatings for arduous anti-corrosive service”
Experience the progress.
Subsea Offshore Crane Technology Max. capacity - main hoist up to 300 to in air Max. radius up to 50 m Subsea capability down to 3400 m Totally new Subsea Winch Concept Predicted AHC-System
Liebherr-Werk Nenzing GmbH Dr. Hans Liebherr Str. 1 Tel.: +43 50809 41-481 Fax: +43 50809 41-625
offshore.crane@
liebherr.com www.liebherr.com
Offshore Marine Technology 1st Quarter 2013 15
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