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Why Galvanized Tubing

Steel Tube Coatings

Coatings: What do they do for our products?

Coatings add to the life of our products by providing longer durability against normal environmental corrosion. Coatings improve the appearance of the tubing, and they prepare the tube surface for specific end uses. galvanized tubing used for greenhouse structures

What is so special about Allied's coatings?

The technology and the process of carbon steel tube and pipe manufacturing are well known to the hundreds of manufacturers across this nation and in other countries. But what makes Allied so special is our ability to combine the following two functions with a high degree of success. Developing unique coating systems/formulations especially for Allied's products and processes. Developing unconventional coatings application equipment and techniques to facilitate continuous on-line coating application and curing operations at high line speeds.

Exterior Coatings Classifications

playground equipment made with galvanized steel tubes Unless otherwise specified by a customer, almost all of our galvanized tube and pipe is triple-coated externally by using the following three sequential processes:

  • Galvanizing (zinc coating)
  • Conversion coating (for passivation film)
  • Clear organic polymer application
  • Zinc Coating

Allied uses special high-grade quality zinc for its galvanizing operation. Our zinc is 99.99% pure and contains only a trace amount of lead. Hot-dipped galvanized pipe or pipe made from pre-galvanized steel coils normally use Prime Western grade zinc and other grades which contain a high level of lead, sometimes more than 1% by weight.

Conversion Coating

The conversion coating over the galvanized surface is formed due to a chemical reaction and this film becomes an integral part of the superficial layers of the zinc coating. The film passivates the highly reactive zinc surface and retards the formation of white rust by a substantial margin. Also, the conversion film enhances bonding or adhesion of any additional paints or coatings applied over the galvanized surface. For small mechanical tube, where a silver bright type of surface is more desirable for some of our customers, a minimal amount of the conversion coating is applied for short-term indoor storage purposes. For the relatively larger diameter pipe, a heavier coat is applied.

Clear Organic Polymer Coating

The clear organic polymer coating is applied as a third coat or final finish on the exterior surface. This final layer acts as a barrier coating and further reduces the atmospheric corrosion of the product. However, there is an interesting phenomenon that occurs as a result of the combination of the second and third coating. Combined performance (corrosion protection of these two coatings) is more than the summation of the individual protection provided.

Zinc Interior Coatings

We have a number of ID (interior diameter) zinc coatings, which have been specially formulated to meet specific customer fabrication requirements. We are continuously upgrading our ID coatings to maximize the overall corrosion resistance of the interior of the tube. All our ID coatings are applied after the tube is welded...thereby assuring a uniform coating on the entire interior surface. In addition, none of our ID coatings will contaminate paint or powder coat cleaning systems.

galvanized steel pipe cross section to show flo-coat, chromate conversion coating, clear polymer coating

Looking for more on why you should use galvanized tubing in the first place? We've got plenty of information in our Literature Library, or you can dive right into some specific product information such as Flo-Coat ® Steel Tubing or Gatorshield ® coating. Our Sonco Tube professionals are standing by to provide additional information or to provide a free quotation for your next tubing project.

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