Can You Paint External Metal in Cold Weather?

Temperature and moisture are known to affect paint application, so painting architectural metal in cold weather and rain should be avoided. Ideally, recoating metalwork in interiors is best done during the winter when inclement weather will not affect projects as it does on exterior work. However, if winter is the only time for refurbishing exteriors, you can paint external metal like on the shopfront framework in cold weather, but there are guidelines regarding painting in the rain and in extreme cold.

Why is it Difficult to Paint Metal in Cold Weather?

Frost on metal surfaces can cause problems when applying new coatings. In particular, a coating will not adhere to a frosty substrate. Even if the new coating does stick, if frost is not removed before applying a fresh coat of paint, the moisture trapped underneath the coating can cause it to fail prematurely.

Paint cures within specific temperature ranges and the time it takes to harden depends on the type of coating. If it is too cold, then the paint will not cure, and if it is soft for too long, then it loses its protective properties and will be prone to dents. Cold and damp conditions prevent the formation of an adequate paint film which can mean the paint will fail in quite a short amount of time. This is because when the coating doesn’t coalesce thoroughly damp seeps into the uncured paint. Then when this moisture evaporates, certain elements reach the surface and stain it. Consequently, rust may leach through to the top, and mildew can become problematic.

The actual process of spray painting is also much more difficult in winter. Temperature affects the viscosity of liquids and paints become thicker and more difficult to apply in very cold weather. In extreme cold, the paint can actually freeze which would make it impossible to apply. If paint has been applied, but freezes before it has dried then this will also cause problems.

It is not just the coatings and their curing that are disrupted by extreme cold, the sprayers are also effected by winter. Operatives cannot work in extreme cold for long periods of time and are also not as agile in very low temperatures. This means that projects may take longer than they would in summer months which is another reason why it may best to postpone the refurbishment of external metal. After considering all these possible difficulties, the first thing to establish is whether it is really necessary to recoat the metalwork during colder months or can it wait until the spring? If the work has to be done in winter then the following tips may be helpful and a good onsite spraying company should follow these guidelines.

A Guide to Painting Exterior Metal in Cold Weather

• Make sure any moisture is removed from the surface and remember that damp may not be visible in sub-zero temperatures. Frost might have to be scraped off and the surface wiped down, so that moisture isn’t trapped underneath the coating once it has been applied.

• Check what the temperature range needs to be for the specific coating to cure. Some 2-pack paint systems have separate curing agents that work in very low temperatures.

• Ensure an adequate amount of induction time is set aside for cold-cure paint systems. The induction time is the period of time the paint must be left for after it has been mixed with the curing agent. This is to allow the chemicals to react with each other fully, so that the coating will harden properly.

• If the curing time increases in low temperatures make sure the newly coated surfaces are protected, so the paint doesn’t become marked while it is still soft.

• It may be necessary to heat up the substrate in order to avoid some of the aforementioned pitfalls. This can be achieved by building a tent and using supplemental heat within it. Take care to measure the temperature of the metal itself rather than the air temperature as the two may differ.

• Even if the paint is applied when the temperature is at an ideal point, you should ensure that colder weather has not been forecast for at least 48 hours after application.

It is advisable to focus on restoring interiors rather than exteriors during winter, though you can paint external metal in cold weather. With a little know how and the right materials, winter shouldn’t hinder refurbishment projects too much if at all.