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Powder Coating Finishes for Steel and Aluminum Light Poles provides insight into how powder coating is used on steel and aluminum light poles. The paper concludes with an overview of DWM Holdings’ powder-coating process and suggested maintenance to prolong a powder-coated finish in the field.

The finishing or coating of articles is not new. Early man coated the walls of his cave to enhance their appearance and sought to increase the life and durability of his domestic products by overcoating or water proofing them with materials at hand, applied by any method available.

To meet the challenges set by our competition and continue our emphasis on quality and service, we use a thermosetting polyester powder coating process to improve the outdoor exposure requirements of our steel and aluminum lighting standards. Advances in materials and application technology, along with the search for the elusive “perfect coating,” require constant attention toward improving the way we finish our products.

All of our products come complete with our state-of-the-art, multi-stage finishing process.

Mechanical and Physical Properties

Our finishing process varies depending on the warranty selected, but, at a minimum, all products receive the following:

Stage 1: Cleaning

The overall success of our finishing process depends entirely on the quality of the product at the beginning of the process. All products are first inspected for visible deposits of oil, grease, or other contaminants. Surface imperfections such as sharp fins and edges, weld spatter, or burning slag are removed. Once any visual imperfections have been addressed, the piece is sent to our four-wheel shot blaster system, specifically designed for the cleaning steel and aluminum poles. We use steel shot to remove any rust, mill scale, oxides, or other unwanted particles from the shaft or bracket. Upon exiting the shot blaster, compressed dry air is used to remove any remaining shot. The quality of our inspections, shot, and equipment result in a surface preparation that exceeds the specifications published by the SSPC-SP10.

Stage 2: Phosphate Rinse (Steel Poles Only)

In this stage, the pole is coated with iron phosphate, which creates an iron oxide base followed by a flat or amorphous metal phosphate topcoat. This phosphating, or conversion coating, is a critical part of the pre-treatment process for steel poles, adding significantly to the performance of the finished coating. A phosphate coating converts the metal substrate to a uniform, inert surface, which improves bonding, minimizes the spread of oxidation if the coating is scratched, and improves the overall corrosion resistance of the final part. The phosphate solution sits directly on the pole before being rinsed off prior to the pole going into the dry-off oven.

Stage 3: Powder Coat Application

Powder coating is a durable scratch- and chemical-resistant finish that provides excellent corrosion protection from environmental elements. Powder coating is also an environmentally friendly process that emits nearly zero volatile organic compounds (VOC). Whether it be standard or custom colors, our powder coat finish is one of the finest in the industry.

The powder we use is a triglycidyl isocyanurate (TGIC) polyester specially formulated for Lyte Poles. This formula consists of polymers, pigments, and fillers that form a fine dry powder for electrostatic application. The electrostatic application is performed automatically by the negative charging of the powder at high voltage, low amperage, and electrically grounding the pole. This creates a magnetic effect that enables the powder to be applied consistently and uniformly to all exposed surfaces of the pole. Powder coating provides superior edge coverage and creates a high-quality, durable finish with virtually no drips, runs, or sags.

Stage 4: Curing

We cure our powder using a unique combination of infrared and convection heat. The pole is heated to temperatures exceeding 450°. When the powder is exposed to this heat, it begins to melt, flows out, and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This curing process, called crosslinking, requires a certain temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed.

Stage 5: Blue Wrap

Once completely cooled, the pole is then wrapped in Lyte Poles’ signature Blue Wrap — a multi-layered, UV- and tear-resistant, vinyl bubble wrap designed to ensure the products reach the job site in top condition.

Additional finishing stages such as galvanizing and adding an interior rust inhibitor are available through our extended 5- and 10-year warranties.