Galvanized Fabrications are Hot-Dip Galvanized for Long Lasting Protection
Materials Suitable for Galvanizing
Most iron containing materials are suitable for hot-dip galvanizing. Hot rolled steel, cold rolled steel, cast steel, ductile and cast iron will have enhanced service-life after hot-dip galvanized. Structural steel shapes, including those of high-strength (under 150 ksi/1100MPa) and low alloy materials are hot-dip galvanized after fabrication to obtain long lasting protection. Different steel chemistries will affect the appearance of the galvanized coating, but do not negatively affect the corrosion resistance. The elements of carbon in excess of about 0.25%, phosphorus in excess of 0.04%, or manganese in excess of about 1.3% will cause the production of thicker matte coatings. Silicon levels less than 0.03% or between 0.15 and 0.25 is desirable for the best cosmetically appealing finish on your product.
Allowing for Proper Drainage
For effective galvanizing, cleaning solutions and molten zinc must flow without undue resistance into, over, through and out of the fabricated article. Where gusset plates are used, generously cropped corners provide for free drainage. If cropping gusset plates is not possible, holes at least ½" in diameter must be placed in the plates as close to the corner as possible. To ensure unimpeded flow of solutions, all stiffeners, gussets and bracing should be cropped to a minimum of ¾". Provide holes at least ½" in diameter in the end plates on rolled or formed shapes to allow molten zinc access during immersion in the galvanizing bath and drainage during withdrawal.
Tubular Fabrications & Hollow Structural
As with all steel, pipe and other hollow materials must be thoroughly cleaned before the molten zinc will metallurgically bond with the steel.
Mill coatings like varnish and lacquer, in most instances, cannot be removed at the galvanizer. These coatings should be blasted clean from pipe before arrival at the galvanizing plant.
The primary reason for vent and drain holes is to allow air to be evacuated, permitting the object to be completely immersed into cleaning solutions and molten zinc. Proper sizing and location of vent / drain holes, make it safer to galvanize and provide optimal finish inside and out.
Remember that protection against corrosion begins at the drawing board. It must be factored into the product's design. Certain rules apply when designing components for galvanizing. These rules are readily followed and, in most cases, are simply those that good practice would dictate to ensure maximum corrosion protection.