Painting Guidelines for Galvanized Steel Tubing

Painting/Powder Coating

When you weld galvanized steel tubing, all protective coatings are vaporized, thus leaving a raw, unprotected area in the weld zone. Salt spray tests have proven that powder coating over zinc could increase the product life 4-6 times. For customers who powder coat, and are concerned about corrosion protection in the weld zone, we would like to suggest four cold galvanizing compounds that are heat resistant (up to 750° F) and act as a primer for powder coating. They are: ZRC cold galvanizing compound (battleship gray); ZRC Galvilite cold galvanizing compound (shiny); Rustolastic #24-A-120 (sales code 073258); Kalcor 75% zinc dust epoxy primer #61-2373. Triple coated galvanized tube products are protected by a clear organic top coating which provides excellent adhesion properties to most thermo-set powder coatings, as well as to the following air dry and bake topcoats.

Best Paints for Galvanized Steel Tubing with our clear organic top coat:

Paints requiring individual evaluation:

Cleaning Triple Coat Tubing Prior to Powder Coating

Our unique in-line triple caoat process provides an excellent finished tube surface which can be readily post-coated with either a powder or a liquid coating application and curing process. The manufacturing process applies three layers of protection on the steel tube; zinc, conversion coating, and a clear priming polymer, resulting in a clean and ready-to-coat tube as a final product. The cleaning of the tube surface for post-painting or powder coating is required only for the removal of the surface contaminants deposited on the tube surface during storage, transit, handling, or processing. No additional pre-treatment is required for improving the coating adhesion over galvanized products. Benefits of using our Galvanized Products when Powder Coating If a surface grinding process is required in your powder coating operation, it demands additional manpower and maintenance expenses. With our galvanized products, there is no need for the use of this abrasive cleaning process.

The only cleaning that is required when powder coating over our galvanized tubing is to remove the dust and dirt that builds up during storage, transportation, and handling. A light detergent or simply a warm water wash is all that is needed. If the tubing is not smeared with a greasy or oily film, a simple wiping action does the job.

The clear third coating on our triple coat products acts as a primer for powder coating and liquid coating applications, exhibiting excellent adhesion and abrasion characteristics. For those that require a high-temperature baking process, it is heat-stable for the normal curing cycle (450° for 10-12 minutes). The advantages of using our triple coated products are numerous from the processing point of view. However, the biggest benefit is from the phenomenal corrosion resistance that can be exploited from the synergism of powder coating over the galvanized surface. Recent salt spray tests showed that scribed powder coating over untreated tube peeled 1«” after only 549 hours. No significant creepage was found at 3000 hours on the triple coated product.

Sonco offers a Cold Galvanized Primer & Corrosion Protecting Touch-up Paint.  Click HERE for more information or Contact one of our Tubing Professionals today!