Tech Spec

Technical Information

The quality and durability of galvanized coatings depends, among other things, on the proper selection of steel based on its physical and chemical properties, as well as on compliance with design and assembly standards for structures to be galvanized.
Our customer service team will be pleased to assist you in your galvanizing projects.

Steel Selection

Carbon, silica, phosphorus and manganese are the main elements to consider when selecting steel for a project involving hot-dip galvanizing. The concentration ranges in which these elements must be found are well defined in the ASTM A385 standard. Respecting these selection parameters will ensure that the zinc coating obtained during the galvanizing process will offer effective, resistant and durable protection during the useful life of the galvanized part.

Some steels, such as high strength steels, may be subject to embrittlement during galvanizing. Although not very frequent, it is important to consider the recommendations of the ASTM A143 standard when selecting the steel in order to minimize the risks related to embrittlement.

Galvanizing DEsign

The hot-dip galvanizing process involves the complete immersion of steel parts and structures in a pool of molten zinc. As a result, the design of assemblies intended for galvanizing differs significantly from that of structures and assemblies that are painted.

The design of steel structures and assemblies with ventilation and drip holes that meet ASTM A385 criteria is critical for safe immersion in the galvanizing pool and for quality galvanizing.

4 basic elements that can affect the galvanized coating:

Chart 1. - Drainage holes for overlapping surfaces - steel thickness less than or equal to 1/2" (1.25 cm)

Overlapping surfaces in2 [cm2]

Holes

Non-welded surfaces

< 16 [< 103]

None

> 16 and < 64 [> 103 &< 413]

3/8" [1 cm]

1" [2.5 cm]

> 64 and < 400 [> 413 & < 2580]

1/2" [1.25 cm]

2" [5 cm]

each increment of 400 [2580]

3/4" [2 cm]

4" [10 cm]

PREVENTION

Some applications require the assembly of steel parts of different sizes and thicknesses, while others require large quantities of welds, creating many residual thermal constraints in the assembly.

In such cases, the application of the recommendations stated in the ASTM A384 standard makes it possible to orient the design and fabrication in such a way as to minimize the risks of deformation and distortion that would occur during the galvanization process. A design that respects the spirit of the ASTM A384 standard combined with the know-how and expertise of the galvanizer are the key ingredients to the recipe of success for flawlessly galvanized product.

POST-GALVANIZING

Although galvanized steel's look is increasingly popular, including for residential applications, you often still need to paint galvanized steel. Thankfully, this is a popular practice, and its technique is usually mastered by paint professionals.

Here is an overview of what needs to be followed for post-galvanizing painting. The following content addresses surface preparation when painting galvanized steel. Why paint?

The first answer that comes to mind is "for the look"! Paint can simply be required by the architect, but it can also be used for identification purposes or as extra protection in a harsh environment. Painting galvanized steel is known as a duplex system. The benefits are...

Paint acts as an additional barrier protecting galvanized steel;
Galvanizing’s corrosion protection properties are enhanced and optimized by applying paint;
Paint scaling is reduced due to the underlying galvanized steel;
Together, galvanizing and paint offer longer-lasting surface protection;
Combined service life is 1.5 to 2.5 times their individual service life.

Galvanized steel goes through an oxidation (or aging) process that is illustrated with the help of what is called the "passivation cycle." When should paint be applied?

Galvanized steel has three (3) “aging stages” (when oxides are present) and paint can be applied at any stage, provided that there is proper surface preparation…

Immediately after the galvanizing treatment
When the galvanized steel is at 50% of its service life
When the thickness of the galvanized sheet is ≤1mils
At the first sign of rust spots

Frequently Asked Questions

The following is a list of questions commonly asked by our clients. Please contact us if you have a question about our process that is not answered below.