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How to Clean Common Contaminants on Painted Steel Buildings

Something that surely makes steel buildings for sale more attractive to buyers is a fresh coat of paint. Sadly, paint does not stay fresh. Over time, a number of contaminants compromise the quality of the paint, making a cleanup absolutely necessary. Painted steel buildings can only be cleaned properly if the contaminants are identified. Found below are the common contaminants found in painted steel buildings and how these should be cleaned.

Dirt There are two main types of dirt that can be found on painted steel buildings, and these are dry dirt and organic or greasy debris. Between the two, the latter is more challenging to clean. One need not worry too much about dry dirt because it can be cleaned off by rain; if rainwater cannot remove the dirt entirely, high-pressure water spraying will work.

Clean Common Contaminants

Unfortunately, organic or greasy debris—those that result from pesticides, fireplaces, oil from ventilation fans and auto mobile exhaust—are not easily washed off by rainwater. Water alone will not remove these too. To make matters worse, this kind of residue keeps other contaminants on the building surface as well. Cleaning this kind of dirt requires the use of ammoniated cleaners, solvents and detergents.

Naturally, dirt is more apparent with lighter paint colors. Polyester and SMP (silicone-modified polyester) keep more dirt than other materials. Chalk The white substance is actually a by-product of the deterioration of the paint system due to ultraviolet light (UV) exposure. Thus, chalking is a major problem for areas and parts of the building that are directly exposed to the sun. After a couple of years, a white chalky film will cover the painted surface, causing the gloss of the paint to become dull and the color to become lighter. Chalk accumulates on the surface because rain washes it off, but not completely; the residue left is what causes the buildup.

The amount of the buildup will depend on the type of pigment color and resin found in the top coat. Plastisol’s chalk more than polyesters, SMPs and fluorocarbons. Unlike dirt, chalk is more apparent with darker paint colors. Just like dirt, chalking can be removed with high-pressure water spray. Biological growth/mildew This is tougher to clean than the aforementioned two because it involves growth—the likes of mildew do not just accumulate on the painted surface; it grows on it. It grows on surfaces that remain damp due to lack of sun exposure, such as those under eaves or sheltered areas. Mildew can also grow atop layers of a dirt build up if said build up is kept moist.

Mildew must be removed as soon as possible because by-products of biological growth are corrosive. First, the surface should be wiped or washed with a power spray. Then, the growth should be removed with an antiseptic cleaner like bleach. Afterwards, the area must be rinsed and dried thoroughly. The cause of the growth must be addressed to prevent mildew from growing again.

Bleach must be handled with care because it is corrosive and toxic. It should not be mixed with other cleaners, though it can be used along with premixed laundry detergents.

Rust to effectively clean rust from a painted steel surface, one must know what kind of rust there is to clean and understand its cause. For instance, rust that resulted from a run-down of steel debris that remained on the building after erection can be removed by simply removing the said debris. Also, rust stains that are the result from the run-down of a higher rusting panel should be removed by first getting rid of the rusting panel and then cleaning the affected area.

The cleaner recommended for rust is a phosphoric acid-based one. The strength of the cleaner to be used should depend on the severity of the rusting as well as the exposure to the building. Lower concentrations eliminate the rust slowly, but they can remain on the steel building for long without damaging it. Higher concentrations work faster, but they need to be rinsed off immediately and thoroughly; if left for a long time, the metallic coatings may be damaged. Muriatic acid is never recommended for cleaning rust on steel buildings because of the damage it can cause.

Graffiti Removing graffiti is tricky when pre-painted steel buildings are involved. This is because the job will involve eliminating the paint of the graffiti without eliminating the original paint. An aggressive solvent can be effective in cleaning graffiti off a painted surface, but this should not be left on the surface for too long. Testing on a hidden area of the building should be done to see how the solvent will react to the paint. If the strong solvent fails to remove the graffiti, the surface needs to be repainted.

This article was written by Michael Harrington. The author, who has written countless articles about steel building design and assembly, now contributes content for Steel Buildings Design.

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