One of the primary reasons for coating steel structures is to help prevent and reduce corrosion. The type of coating used is a vital aspect of the process. Another important aspect is surface preparation. Improper surface preparation will lead to premature failure, regardless of the coating system being utilized.
There are several surface conditions that must be remedied with proper surface preparation. One significant one is how slippery the surface is. The smoother a surface is, the more difficult it is to achieve proper bonding with your chosen coating system. For example, paint on glass resists bonding and is easily cleaned; paint on a rough surface like sandpaper is very difficult to remove.
Another condition that must be remedied is debris on the surface. This can be simple dirt and dust accumulation. It could be chemicals, such as solvents or oil, which will impair bonding. A serious form of debris is soluble salts, such as chlorides and sulfates. These are invisible to the eye, but will cause a coating to fail almost immediately by drawing moisture through the coating as it cures.
There are three basic steps to surface preparation. The first is to remove the loose debris such as dirt and dust. The second is to remove oils and chemicals through the use of solvents, cleaning agents and appropriate chemicals. The third is to abrade the surface either by hand, with power tools or, in some situations, by blasting agents.
The methods utilized will depend on several factors. Is the surface new or has it been in service and exposed to environmental factors? What type of coating system will be used? What is the environment of the structure like? Are you doing warehouse painting or equipment painting? These and other issues will determine the extent to which the surface must be prepared.
Proper preparation will ensure that your new coating system will last for many years, and maximize your investment. Industrial painting contractors understand the need for extensive preparation and will include those costs as part of their bid package. It is necessary for facility managers to understand this reality as well, so that they will not be tempted to try and save money by reducing preparation time.