The five steps of coating selection

Acrylics, alkyds, epoxies, high gloss, rust inhibitors, direct-to-metal. The options when selecting coatings can be overwhelming, and with maintenance dollars at a premium, making the correct choice is critical. So how do you wade through the sea of coatings and arrive at the one that addresses your needs without breaking your facility’s budget?  Taking a methodical approach and answering a few simple questions can make this daunting task much more manageable and may help you avoid selecting the wrong coating.

One: What do you want to do?
Although your first instinct is usually to say, “Make this look better,” this may not be the top priority. If the project is in a high-visibility area where a brilliantly colored, high-gloss surface is expected, then a coating system that delivers long-lasting sheen and color is critical. Avoiding bright colors that fade under UV exposure is important here, so epoxies may be a bad choice, since they tend to “chalk” with long-term exterior exposure.

On the other hand, if a rusted surface is unsightly but a loss of strength from corrosion is the greater concern, then surface protection should take the lead. Corrosion protection is typically achieved one of three ways: a barrier coat for corrosive elements, an additive to inhibit corrosion, or a sacrificial surface to corrode instead of the substrate.

Two: What is the environment?
The UV exposure of exterior surfaces is one of many factors that can affect the performance of a coating. Extreme heat or precipitation are also factors, and if your facility is located in a coastal area, airborne salt particles may also wreak havoc on your coating. Road salt that is used during the northern winter months can be just as damaging. The chart (below) can help  you measure how corrosive your environment is. The more checked boxes on the left, the more corrosion resistance you will need. Epoxies, polyurethanes and zinc rich coatings offer the strongest durability, followed by alkyds and then acrylics.

The impact of continual use is also critical in evaluating performance needs. Floors that must withstand heavy foot and forklift traffic require heavy-duty coatings. Surfaces that undergo repeated scrubbing or constant friction or contact must be coated with a highly tolerant paint. One common way to protect essential areas while reducing overall coating costs is to paint walls halfway or two-thirds of the way up with abrasion-resistant coatings and then apply standard coatings to the rest.

Three: Surface preparation
Surface preparation is a large portion of a project’s cost, and can  triple the overall spend on a job. The ideal surface — new metal with no rust bloom — is a rarity. You are more likely to be painting bare, worn surfaces or substrates that have been painted previously. Blasting the surface back to a bare metal offers the best painting surface, but other options can also ensure good coating adhesion.

Before selecting a surface prep method, decide your total budget for the project (including the cost of labor, equipment, and coatings), and whether or not your facility will be shut down for the project. You will also need a realistic estimate of the life of the new coating.

Once your analysis is done, consult your coatings supplier on the surface prep requirements of various coatings and let them propose some options to get the job done.

Most analyses arrive at a need for  mid-level surface preparation. Regardless of the method you choose, the surface you are painting must always be clean, dry, and dull.

Four: Application options
Does your job consist of simple touch-up to small areas?  If so, you can probably apply the coating with a brush. Select a thin, fluid coating that will smooth out on application. Larger areas often call for application by roller, which speed the job and minimize visible brush strokes.

Finally, if you want to apply a coating quickly, have skilled applicators and the time to cordon off the area, you may want to consider spray application. Spraying takes less time and allows you to apply heavier coats with fewer marks. However, inexperience can lead to runs and sags in over-applied areas and under-application (and eventual coating failure) in others.

Some applications dictate the method by which they are applied. Concrete floors usually require roller application, followed by a spiked roller to rupture air bubbles. High warehouse ceilings are easily painted with dryfalls, which require spray application. Your coatings supplier or the product data sheet will outline the application methods that best suit your project.

Five: Select your coating
If you have followed the first four steps, the selection process should be easy. Your substrate will be the initial determining factor in your coating options.

To learn more about specific substrate requirements and environmental factors, click here to read the extended version of this article. 

This article appeared in the June/July 2005 issue of MRO Today magazine. Copyright 2005.

Back to top

Back to Uptime archives