powder coatings

Galvanized steel versus powder coatings for outdoor environments

Thursday, April 13, 2017

Chipping, fading and corrosion are common concerns when deliberating over the use of galvanized steel coating or powder coating for outdoor furnishings, such as handrails and guardrails, bike racks, playground equipment and park benches. Both coatings; however, are quite different in how they protect components and how they are manufactured. Here, Larson Electronics offers guidance on their unique advantages.

Galvanized Steel Coatings (HDG)

Galvanization is the practice of dipping steel in hot, molten zinc, and a ‘metallurgical bond’ should form between the zinc and steel. This process helps steel-based structures last longer (about 50 to 100 years) at a corrosion rate of 1/30 of bare steel, and is low-cost in terms of maintenance and first-time and lifetime costs.

“Galvanization offers cathodic protection for steel,” notes Andrew Holland of Larson Electronics. “When exposed to moisture from outdoor environments, zinc corrodes very slowly, protecting the base metal – even if small parts of the surface succumb to rust. This streamlines maintenance, as reapplication of coatings is not needed with the zinc layer present.”

Powder Coatings

Powder coating is an organic process that involves barrier-layer protection. An electrostatically charged coating is applied to the surface – specifically a positive charge to the dry powder (thermoplastic or thermoset polymer). This bonds with the negatively charged surface of the base component, creating a rich protective layer.

There are copious benefits of this coating. For instance, it takes about 20 minutes to complete and layers don’t hinder the flexibility of the base item. This helps components endure vibration, chipping, fading corrosion and rough weather. Aesthetically, Holland notes that powder coating is applicable to products that require coloured finishes or textures.

When exposed to outdoor or marine environments, powder coatings can resist corrosion, abrasion and chemicals – but only up to a certain threshold,” adds Holland. “Compared to paint, this type of protection is exponentially more reliable. To ensure protection, powder coatings must be maintained properly by applying paint over the exposed or chipped surface.”

For more guidance, ISO 12944 is an international standard on corrosion protection of steel structures by protective paint systems. It consists of several parts. Holland says that for marine locations, such as coastal areas, users must refer to category C5-M. ISO 12944 guidelines for C5-M marine environments recommend the application of zinc-rich primer, epoxy intermediate or polyurethane to ensure durability for at least 15 years.

6 thoughts on “Galvanized steel versus powder coatings for outdoor environments

  1. We have a large, outdoor deck job with many feet of custom railings. We want to specify galvanized for a “modern industrial” look. Client likes idea, but is cost sensitive. Which is typically less expensive: galvanized or standard-color (black) powder coat? Thanks

  2. Yes, I agree with you .Zinc reacts with moisture or oxygen slowly as compared to other elements which helps the machinery or other equipment to be safe from corrosion. Galvanized Steel Coatings is best for marine equipment where there is so much moisture and its maintenance is also not needed .Thanks for the article .

  3. I want technical details why galvanized is better than powder coating

    Which application is more durable for exterior areas like shades, bench, signage etc etc

    • I’m interested in a response to this question as well. We are a signage, wayfinding & graphics design firm and are doing an ocean-front resort in Southern California. Owner is asking for the most durable option.

  4. We are planning a steel base to be used with a quartzite top for a patio table. The stone will weigh approx. 350lbs. One ornamental metal fabricator suggested galvanizing and then powder coating. Is this belt and suspenders or does it make sense?

    Thank you.


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