Causes and Solutions to Your Outdoor Metal Paint Failures

Spray paint is used on a wide variety of outdoor metal structures from store fronts, to sculptures, to library drop boxes. However, outdoor painted surfaces can often fail to maintain their freshly painted look and turn into eyesores. At Spray Finishes, we’re outdoor metal paint experts and we wanted to tell you about some common outdoor metal paint failures, what causes them, and provide simple solutions.


  • What is it? Blistering is when small air bubbles form between the coating of paint and the metal surface underneath.
  • What causes it? This issue can arise when solvent-based paints are sprayed onto a surface that is too warm (above 85 degrees Fahrenheit). This is called solvent boil. More likely causes of blistering include applying a too-thick coat of paint and/or applying a second of paint before the first coat has fully dried. This is because the solvent becomes trapped and expands, thus creating the blistering effect.
  • What’s the solution? To prevent blistering, make sure you are applying the right amount of paint to the surface. Use enough to cover, but there’s no need to saturate the surface. Give the paint at least an hour to dry before applying the second coat. And make sure that the surface you are painting isn’t too hot.


  • What is it? Over time, paint on metal surfaces can erode, causing the paint to decompose into a chalky surface layer, which will appear bleached and feel loose and powdery to the touch.
  • What causes it? The biggest cause of paint decomposition is sunlight. UV rays causes all paint to break down over time.
  • What’s the solution? Your best defense against chalking is to use high-quality exterior-grade primers and paints that are specially formulated for metal. Also, keep in mind that dark colors absorb heat and light and may therefore become chalky more quickly than light colors. So, if you are painting a structure that gets a lot of sun, consider using a lighter color.


  • What is it? Sometimes outdoor metal paint can split and cause cracking or flaking. Usually, hairline fissures can be detected before full-blown cracking sets in.
  • What causes it? This unsightly problem is caused by low-quality paint that lacks flexibility and adhesion. Another reason for cracks or flakes is an unproperly prepared surface.
  • What’s the solution? First, make the investment in a high-quality paint. It’ll cost more, but you’ll get much better, longer-lasting results. Also, don’t take shortcuts when it comes to prep work. Make sure all old paint is removed and you use a high-quality primer.


  • What is it? Dirt refers to natural mud or soil splashed onto your painted surface, air pollution build-up, or even food and beverage spills.
  • What causes it? Dirt and pollution have countless causes and are a fact of life, unfortunately. If not dealt with, this can degrade your painted surface.
  • What’s the solution? We certainly can’t eliminate dirt and pollution, so your best bet is to again use a high-quality paint. Dirt and stains are much more likely to adhere to surfaces covered in cheap paint. Also, get a paint that will withstand washing, so you can clean off the surface as needed.

Mold or Mildew

  • What is it? Mold is fungus that sprouts form tiny spores that float about in the air. Mildew is a common type of mold that loves to grow in damp, dark spaces.
  • What causes it? Spots of brown, grey, or black mildew can appear on coated surfaces that are damp and do not receive much sunlight.
  • What’s the solution? You can use a mold-resistant paint, which will help. Also, if possible, make sure that the surface you paint gets lots of sunlight. Finally, if you do detect mold or mildew, wash it away with a mild bleach solution. If not dealt with quickly, it will just continue to grow.

All of the tips and techniques above will help keep your outdoor metal paint looking its best. Also, consider electrostatic spray painting offered by Spray Finishes for any of your metal painting projects. The electrostatic process uses magnetism to guarantee a smooth, clean finish that prevents all of the common outdoor metal paint failures.

Spray Finishes, a division of Stone Services, has been in the electrostatic spray painting business since 1938. They specialize in on-site painting, and also have a 10,000 square foot shop for large off-site jobs. Spray Finishes’ friendly and knowledgeable staff is ready to serve you at any of their five tristate area locations, including New York, New Jersey, Connecticut, Long Island, and Westchester. Contact Spray Finishes today for an estimate on your next painting project.

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