What is Paint coatings for steel?
What is Paint coatings for steel?
Paint coatings for steel structures have developed over the years to comply with industrial environmental legislation and in response to demands from bridge and structure owners for improved durability performance. A paint consists of a pigment, dispersed in a binder, and dissolved in a solvent. The most common methods for the classification of paints is either by their pigmentation or by their binder type.
A modern paint system usually comprises a sequential coating application of paints or alternatively paints applied over metallic coatings to form a ‘duplex’ coating system. Protective paint systems usually consist of primer, intermediate/build coats and finish coats. Each coating ‘layer’ in any protective system has a specific function, and the different types are applied in a particular sequence of primer followed by intermediate/build coats in the shop, and finally the finish coat (or top coat) either in the shop or on site.
Prefabrication primers are used on structural steelwork, immediately after blast cleaning, to maintain the reactive blast cleaned surface in a rust free condition through the fabrication process until final painting can be undertaken. These types of primers are not used before the application of thermally spraying coatings.
The method of application of paint systems and the conditions of application have a significant effect on the quality and durability of the coating. Standard methods used to apply paints to structural steelwork include application by brush, roller, conventional air spray and airless spray/electrostatic airless spray.
Airless spray has become the most commonly used method of applying paint coatings to structural steelwork under controlled shop conditions. brush and roller application are more commonly used for site application, though spraying methods are also used. ‘Stripe’ coatings applied to edges and sharp corners are usually applied by brush.