Well-documented years of experience have proved the benefits of hot dip galvanized protection. At least 10-20 years are commonplace in industrial and marine environments, more than 25 years (frequently much more) in rural atmospheres.
When maintenance eventually becomes necessary, it is straightforward: no complex preparation treatments are necessary.
For many applications the cost of galvanizing is lower than that of applying alternative coatings. Furthermore, galvanizing has been getting steadily cheaper compared with painting.
The reason is simple: alternatives - particularly painting - are very labour intensive compared with galvanizing which is a highly mechanized, closely controlled factory process.
Low initial cost and long life make galvanizing the most versatile and economic way of protecting steel for long periods (20+ years).
There are bonuses from no maintenance or extended maintenance intervals: fewer problems of access in remote areas, difficult terrain or when buildings are closely packed together; also when there are safety restrictions e.g. electricity pylons.
The process is relatively simple, straightforward and closely controlled. The thicknesses (weights) of coatings formed are regular, predictable and simply specified. Galvanizing is one of the few coatings which is completely defined by a British Standard (BS EN ISO 1461).
A full protection coating can be applied in hours; a complicated paint system can require a week.
Galvanizing is unique: the hot dip process produces a coating which is bonded metallurgically to the steel. No other coating process has this feature, and as a result galvanized steel has by far the greatest resistance to mechanical damage during handling, storage, transport and erection - an important factor where steelwork is to be shipped around the world.
Because it is formed by dipping steel in molten zinc, all parts of the surface of the steel are coated - inside, outside, awkward corners, and narrow gaps which would be impossible to protect in any other way.
The coating actually tends to build up at vital corners and edges - rather than thinning out as do brushed, sprayed and other dipped coatings.
Galvanized coatings protect steel in three ways.
Firstly, the coating weathers at a very slow rate giving a long and predictable life.
Secondly, the coating corrodes preferentially to provide cathodic (sacrificial) protection to any small areas of steel exposed through drilling, cutting or accidental damage; scratches are sealed by weathering products from the zinc.
Thirdly, if the damaged area is larger, the sacrificial protection prevents the sideways creep of rust which can undermine paint coatings.
Galvanized steel simplifies inspection of the protective finish. The nature of the process is such that if the coating looks continuous and sound, it is! Thicknesses - simply specified through BS EN ISO 1461 - can be easily checked with an electronic probe.
Galvanized steel is ready for use. No further site surface preparation, painting, touch up or inspection is necessary. Once erected the galvanized steel is ready for use: and cladding can begin immediately, thus accelerating the construction programme.