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Benefits from coating architectural steel

The idiom, "if a tree falls in the forest but nobody is around to hear it, does it make a sound?" was a scientific thought experiment or philosophical allegory, depending on whom you're speaking to.

The version I'd like to ask is: if hidden architectural steel is powder-coated, does it matter? After all, one reason for powder coating metal is aesthetic—coating metal with powder results in beautiful pieces typically installed in areas where people see them.

What would be an excellent reason to powder coat something nobody sees? I'm glad you asked!

Advantages of Powder Coating

Steel being powder coatedAs we've discussed in "The Familiarity and Strength of Powder Coating," there are eight advantages for using powder coating:


  • You only buy the amount of powder coat needed
  • Powder coating is cheaper than wet paint
  • If it's not contaminated or damaged, it's recyclable
  • We can reuse it after reclaiming it for future applications
  • It eliminates extra steps and extra drying time


  • Powder coating is long-lasting
  • Surfaces are resistant to chipping, fading, scratches, or wear
  • Color remains durable and lasts longer
  • High resistance to moisture, chemicals, impacts, and weather
  • Passes salt spray testing

Efficient Process

  • Waste is reduced because of the electromagnetic charge. The powder adheres to the metal.
  • The spray nozzle uses only the amount of powder needed.

Curing and Drying

  • Less time needed for curing, processing, and drying compared to wet paint applications
  • Curing takes minutes, allowing for quick assembly and packaging.
  • The powder doesn't contain VOCs or solvents. Heated air is recycled, filtered, and emptied back into the shop.
  • Powder applications need less air and air exchanges compared to wet paint applications.


  • Wide range of colors, finishes, thicknesses, and textures
  • Powder coating eliminates many of the issues facing wet paint applications, such as dripping, sagging, or running


  • Soapy water, rinsed with water, is all that's needed to clean a powder-coated application.
  • No need for special solvents or cleaners.

Environmentally Friendly

  • There are no VOCs, solvents, or other harmful chemicals in the powder, making disposal safe.
  • Lower carbon dioxide emissions
  • No primer is necessary for powder coating applications


  • The finish of a powder coat is excellent. It's evenly distributed, doesn't run or drip.

AAMA Performance Specifications

Example of metal that was powder coated - showing 5 different colorsIn the architectural world, liquid and powder coatings are treated equally. The Fenestration & Glazing Industry Association (FGIA) has written many voluntary specifications regarding testing and performance requirements.

Before it became the FGIA, the American Architectural Manufacturers Association (AAMA) composed those specifications. Despite the new organization's name, it refers to any specifications as AAMA.

AAMA tests coatings to determine how well they last. Many factors are measured, primarily gloss retention, color retention, and paint thickness after drying.

There are three AAMA coating specifications: 2603, 2604, and 2605.

AAMA 2603

The most basic type of coating is those meeting the AAMA 2603 specification. They usually coat ceiling tiles and inside windowsills to meet the 2603 spec. This level protects against scuff marks and wear and tear, but not extreme outdoor weather.

2603 Ratings

Color retention: The AAMA doesn't recommend using 2603 for the powder coating process in Preston, WA on materials that need to keep color over a long period. Their estimate says that it fades after one year of use.

Gloss retention: There is no specification for gloss retention for 2603 rated paint.

Thickness: To achieve a 2603 rating, paint must be a minimum of 0.8 mm.

Accelerated testing: 2603 rated paint must withstand 1,500 hours of salt spray and humidity abuse before becoming damaged.

AAMA 2604

We can find coatings specified to 2604 in high-traffic areas because it's durable. According to Key Link fencing and railing,

AAMA 2604 powder coatings are formulated with super durable or modified polyester resins. This finish provides good color and gloss retention for approximately five years of exposure.

2604 ratings

Color retention: 2604 rated paint must maintain an acceptable level of color change over 5 years.

Gloss retention: After 5 years, 2604 paint must keep 30% of its gloss.

Thickness: To achieve 2603 rating, paint must be a minimum of 1.2 mm.

Accelerated testing: 2603 rated paint must withstand 3,000 hours of salt spray and humidity abuse before becoming damaged.

AAMA 2605

If coated architectural metal needs to withstand harsh weather over a long time, then the metal needs to meet 2605 specifications. The 2605 specification is the highest standard available for organic coatings.

Key Link describes AAMA 2605 as:

… the high-performance exterior specification. These finishes are resistant to moisture, weathering, ozone, and UV radiation.

An application for this finish would include architectural projects that require long-term cosmetic & functional protection (approx. 10 yrs).

2605 ratings

Color retention: 2605 rated paint must maintain an acceptable level of color change over a 10-year span.

Gloss retention: Fifty percent of the paint's gloss must be maintained after 10 years.

Thickness: To achieve 2605 rating, paint must be a minimum of 1.2 mm.

Accelerated testing: 2605 rated paint must withstand 4,000 hours of salt spray and humidity abuse before becoming damaged.

AAMA Testing Process

For meeting AAMA specifications, they test coated panels in many ways. These tests include:

  • Abrasion resistance
  • Adhesion
  • Chemical resistance
  • Corrosion resistance
  • Dry film hardness
  • Humidity resistance
  • Impact resistance
  • Weathering resistance

The AAMA coatings specifications are particularly important when dealing with weathering (exterior durability) performance. To ensure the aesthetic properties of the coating are maintained over time, coated panels are tested in Florida (actually known as Florida testing) for ten (AAMA 2605), five (AAMA 2604), and one (AAMA 2603) year.

Florida weather allows the coatings to be continuously exposed to harsh UV light, humidity, and salt air. After exposure to these conditions, the aesthetic properties, namely color, and gloss are measured.

AAMA Specifications for Paint

Linetec does an excellent job of breaking down the differences of each AAMA specification.

Specification AAMA 2605 AAMA 2604 AAMA 2603
South Florida Weathering
Color Retention 10 yrs: Fade - 5 Delta E 5 yrs Fade = 5 Delta E 1 year: "slight" fade
Chalk Resistance 10 yrs: Chalk = 8 5 yrs: Chalk = 8 1 year: "slight" chalk
1 year: "slight" chalk 10 yrs: 50% retention 5 yrs: 30% retention No specification
Erosion Resistance 10 yrs: 10% loss 5 yrs: 10% loss No specification
Dry Film Thickness 1.2 mils minimum 1.2 mils minimum 0.8 mils minimum
Pretreatment System Chrome or Chrome-Free Chrome or Chrome-Free Chrome or Chrome-Free
Accelerated Testing
Salt Spray 4,000 hours 3,000 hours 1,500 hours
Humidity 4,000 hours 3,000 hours 1,500 hours
Warranty 10 year 5 year 1 year

In Sum

Companies coating architectural metal aren't generous in their efforts. They're not simply making things look good to make themselves look good. Sure, looking at powder-coated metal is much easier than unfinished metal, and that belies the fact those companies are providing value-added services, ensuring its structural integrity.

Although it's very cliché, a chain is only as strong as its weakest link. The same holds for a building or other structure using metal. If a small portion oxidizes, over time, corrosion has a tremendous effect on that structure's overall health. A portion of weakened metal carries that malady throughout the structure, placing it and people in and around it in danger.

Unfortunately, if something falls on a busy street, the noise it makes will be significant.

Showing 1 Comment

Donnie 2 years ago

Great efforts seen on providing an informative blog on steel powder coating. The testing performance and coating specifications are well explained.

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