Hot Dip Galvanizing

THE BENEFITS OF HOT DIP GALVANIZING TO PROTECT YOUR STEEL AND OUR FUTURE

Steel, one of our strongest and most highly versatile materials, is used in countless applications across a variety of industries. Its strength and reliability have been trusted ever since the Industrial Revolution. However, Steel is not without its flaws; a key drawback has always been its susceptibility to corrosion when exposed to the elements. Hot Dip Galvanizing will provide a chemically bonded coating which will provide long term corrosion resistance in almost any environment. Depending on the harshness of this environment, the zinc coating will corrode at roughly 1/30 the rate of bare and unprotected steel.

The Hot Dip Galvanizing process is easy enough to understand, but challenging to master. The process involves a series of coordinated steps beginning with an extensive cleaning process, which may even include sand or shot blasting for severely contaminated steel. Generally, the process begins with placement in a Caustic Solution which removes oil, grease, and other organic impurities. This step is followed by a series of rinses and immersion in either Hydrochloric (HCl) or Sulfuric (H2SO4) acid. Although both acids are effective, Canton Galvanizing uses only HCl acid for a variety of functional as well as Ecological reasons. The acid treatment removes mill scale or the layer of iron oxide on the surface of the steel, thus providing a bare steel surface. Once the steel has been rinsed in water, it is quickly immersed into and removed from the pre flux solution of Zinc Ammonium Chloride. Once dry, the steel is then submerged into a kettle of molten zinc varying in temperature, but generally around 840 degrees F. The zinc interacts with the iron in the steel via a diffusion reaction, thus creating a tightly-bonded alloy coating, that provides superior corrosion protection. Whether exposed to rain or snow, intense heat or buried in concrete, Hot Dip Galvanizing can provide effective, long-lasting corrosion protection, thereby increasing the life of any steel structure.

Key Design Factors

There are a number of fundamental considerations when designing for hot-dip galvanizing. The key components include:

The size of the item that can be galvanized will be governed by the size of the galvanizing bath. Long items can be galvanized by the Double or Progressive dipping process, but items larger than the galvanizing bath in two dimensions cannot be galvanized.
Venting is Vital! If a hollow section traps approximately 18% of its internal volume as air, it will not sink in the molten zinc. Also the trapped air may create a hazardous and explosive situation.
Steel sections of differing section thickness heat and cool at different rates. Unbalanced sections causing differential heating and cooling will increase the risk of distortion (buckling).
Items to be galvanized must be suspended or supported throughout the galvanizing process. This may require holes in some work, or the welding of (removable) lifting lugs.

Key Fabrication Factors

For standard fabrications, a basic set of design rules should be applied. These design steps do not add to the fabrication cost but will ensure a good quality outcome.

Gussets and stiffeners should be cropped.
End plates or base plates on columns- Universal sections should have vent/drain holes in the corners of the web/flange connection and hollow sections should have vent/drain holes in the internal extremities.
Outward facing channels and angles in fabricated frames eliminate the need for vent and drain holes, contrary to inward facing sections.
Terminating bracing short of adjacent flanges eliminates the need for cropping or vent holes.
Overlapping surfaces should be fully sealed.

Capabilities

Our kettle is 21’L x 6’W x 10’D, with this kettle size, Canton Galvanizing can process parts up to 20′ in length. Our spin operation will do small parts up to and including threaded rods and anchor bolts of up to 120″ in length. Special size requests are welcomed and can be accommodated.