Anodising is a process which can last the user decades and in some cases only a few years. The reasons for this are numerous, however five key factors have the greatest influence on the life of an anodised surface.
Coating Thickness Sets the Baseline
Most sulphuric anodising processes can produce a coating thickness of between 5 to 25 microns. This coating is generally suitable for use in light indoor or decorative applications. For more demanding applications a Hard Anodising process can be used. This process can produce coatings of between 25 to 100 microns in thickness. Such thick oxide coatings provide significantly improved abrasion and corrosion resistance. However, the oxide coating will eventually wear away. The thicker the coating the longer the life before it begins to wear away.
Alloy Grade Affects How Well It Holds Up
Different aluminium materials have different properties and thus respond differently to anodizing. For example, the 6000 series of aluminium alloys anodize very well and their oxide layer is very stable. In contrast, high-copper materials (2000 series) form an oxide layer that is much thinner and less consistent than that on other materials. This layer degrades faster. When specifying a material for a part that is to be anodized and have a long lifespan, it is best to refer to the recognised aluminium alloy grades in UK standards.
Mechanical Wear Shortens Life on Moving Parts
Anodising is a very hard coating; however it is not invincible and will wear as other materials do. Hard anodising in particular will show measurable wear on sliding or bearing surfaces within one to three years, depending on use.
UV and Weathering Degrade the Finish Outdoors
Anodised coatings retain their corrosion resistant properties for up to 20 years, however dyed/coloured anodised finishes can suffer from colour loss after as little as 5-8 years, especially when exposed to direct UV. Clear anodised finishes are generally more durable when used in outdoor applications.
Sealing Quality Locks In Corrosion Resistance
The pores of the anodized layer must be sealed following the anodizing process. This is usually done by immersion in hot water or a nickel acetate solution. It is well known that poor sealing is the main cause of early failure of anodized items. More on Anodising can be found at //www.poeton.co.uk/surface-treatments/anodising/.
Regular inspection for signs of wear such as chalking, pitting or colour change can indicate when an anodised finish is coming to the end of its service life.
