Hot-Dip Galvanizing

How we do it

Watch some of our bolts make the journey from plain finish to hot-dip galvanized in this video that describes the process.

Preparation & Cleaning

Cleaning before galvanization

  1. Headed bolts are wheelabrated to remove any excess hot forging scale, then submerged in a caustic soda solution which removes organic material like cutting oil, and then quickly rinsed in water.
  2. Next, the bolts are submerged in sulfuric acid to etch the surface of the steel. This allows the zinc to penetrate the surface layer of the fastener. Again the bolts are rinsed.
  3. The final preparation phase requires the bolts to be submerged in a flux solution which facilitates the reaction of the zinc to the steel.

Hot-Dip Galvanizing

Hot-dip galvanizing

  1. The coating process involves completely immersing the bolts in a tank containing 70 tons of 840°F molten zinc. The material will remain in the tank until the zinc has metallurgically bonded to the steel. This time varies depending on the diameter, steel grade, and a number of other factors.
  2. A crane lifts the material while the zinc is still liquid and a high-speed spinner functions like a centrifuge to remove the excess zinc from the threads. This produces the highest quality threads and trouble-free nut fit.

Inspection & Packaging

Post-galvanization inspection

  1. Parts are water cooled to solidify the zinc and to allow immediate handling.
  2. Each bolt is inspected to ensure all fasteners will take nuts and you will not experience installation nightmares in the field. Product is packaged professionally and clearly labeled for easy identification.

Specialized for threaded fasteners

Galvanizing threaded parts requires a specially designed galvanizing line. General purpose galvanizers will leave excess zinc in the threads, preventing a nut from threading onto the fastener. Portland Bolt’s specialized galvanizing line will:

  • Produce parts faster
  • Ensure clean threads for proper nut fit

Portland Bolt galvanizes threaded fasteners all day, every day in our 12′ long x 4′ wide x 7′ deep zinc tank. Our expertise, specialized galvanizing line, and inspection processes ensure fast delivery times, clean threads, and trouble-free nut fit.


Galvanizing offers an exceptional corrosion resistant zinc coating for steel fasteners. The process provides durability, long service life, and is economical in comparison to other coating options. Portland Bolt’s unique system developed specifically for threaded fasteners ensures quality threads and a trouble-free nut fit.

  • Hot-dip galvanizing offers long-term protection for fasteners and other steel products.
  • Parts are evenly coated for complete coverage.
  • Expected service life can exceed 30 years.
  • Low life-cycle cost makes galvanizing an economical method of protecting steel.
  • Zinc bonds metallurgically to steel providing permanent protection.