Spraying is the most widely adopted method for application of paint systems in a workshop with a controlled environment, often with forced ventilation. Both air-fed and airless spray are possible. Airless spraying is now more common, as application rates are higher and overspray is reduced. Brush application is usually carried out on site, where control of the local environment is more difficult.
Site coating of previously primed steelwork is often preferred by steelwork contractors as it allows the steelwork to be moved rapidly out of the workshop and on to site. The other main advantage is that, as the final coat will be applied on site, repair of damage caused by transport and erection is not required and the finished appearance will be more uniform.
However, a number of important aspects should be considered, as noted earlier:
the quality of the site-applied finish coat will be inferior to that applied in the workshop, particularly if the atmosphere is polluted or in coastal regions (both chlorides and wind-blown sand, for example, can penetrate a considerable distance inland)
all paintwork should be cleaned on site, before application of the site coat on-site coatings should generally be applied by brush damage to paint systems should be minimised by the careful use of strops, wrapped chains or lifting lugs.
The steelwork for the Igus Factory in Germany was blast-cleaned and prepared with its primary coating before being transported to site. The final protective coating was applied on site (see Figure 12.2).
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