G60, G90, ASTM A123 -- what does it all mean?
Many of our customers call with questions regarding specifications.
One of the most common questions we get is regarding G60 or G90
coatings. While these designations do refer to a hot-dip galvanized
process, it is really referring to the continuous galvanizing industry.
These products are usually seen on items like corrugated roofing
and wall panels. ASTM A123 refers to the batch hot-dip
galvanizing process, like we perform daily here at Hubbell.
So beyond that simple explanation, what is the difference?
The 60 and 90 in the G60 and G90 are really referring to
coating weights. G90 products need to have .90 oz/sf of zinc to
meet the specification. This is a total weight for the piece, so it
really means .45 oz/sf on each side. This is equivalent to about
0.75 mils per side. Batch hot-dip galvanizing per ASTM A123
calls for a much higher zinc coating thickness. Standard structural
shapes 1/4" or greater in thickness require a minimum of 3.9 mils
(about 2.3 oz/sf) of thickness. If you compare the numbers, you
can definitely see the difference.
Want more information? The AGA has created a two-page comparison
of the products:
Tuesday, July 30, 2013
Our friends at the American Galvanizers Association (AGA) have put out a new informational video about hot-dip galvanizing. Just click below!
Wednesday, June 12, 2013
Hubbell Galvanizing would like to formally announce that our
new kettle is now operational. The new kettle dimensions
are as follows:
46'L x 5'W x 10'H
Please contact us with any questions regarding size/fit, or to
place your next order -- we look forward to assisting you!
Monday, June 3, 2013
Our customers take a lot of time and pride in their work, and want the completed product to
look its best. We understand this desire, and always strive to make our customers happy.
Quality and appearance are just as important to us as they are to our customers. Below is
a short discussion that can aid our customers in reaching their goal, especially with products
such as handrail.
Raised welds after galvanizing are a common occurrence in the galvanizing industry,
especially with handrail. Many fabricators spend great amounts of time ensuring that the
handrails and welded areas on the handrails are as smooth as possible. These same fabricators
are then surprised when the handrails return from galvanizing and all of the welds they spent
so much time smoothing out, are anything but smooth. Most likely, this has to do with a
differing chemistry between the steel and the weld material -- namely the silicon level.
Some concentrations of silicon can speed up the metallurgic reaction between the zinc and
steel, causing rapid and large crystal growth. This, in turn, causes the welds to become
raised in comparison with the surrounding steel. Fabricators need to pay close attention to
the silicon level of the weld material, to ensure that it is compatible with the steel in the parts
they are constructing. Below is an article from the AGA discussing this issue in more detail:
Tuesday, April 30, 2013
Size and shape of the fabrication is an important consideration to make, during the design process for parts to be galvanized. Because hot-dip galvanizing is a total immersion process, the design must take into consideration the capacity of the galvanizing kettle; therefore, it is wise to verify kettle constraints with your galvanizer early in the design process. Almost any component can be galvanized by designing and fabricating in pieces suitable for available galvanizing facilities. Parts can also be progressively dipped by the galvanizer, to accomodate larger sizes and abnormal shapes. For reference, the average kettle length in North America is 40 feet (13m), and there are many kettles between 50-60 feet (15.24 m - 18.28 m).
If you have any design questions relating to galvanizing, please give us a call:
Friday, April 5, 2013
High-quality castings and forged parts are commonly and successfully galvanized. The quality of the galvanizing is strongly influenced by the quality of the casting. As with all steel to be galvanized, cleanliness is very important to achieve completely galvanized cast iron or steel parts. However, conventional cleaning processes employed by galvanizers do not always adequately clean castings. This is because sand and other surface inclusions are not removed by chemical cleaning. Thorough abrasive cleaning is the most effective method for removing foundry sand and impurities. In fact, the preferred way to clean the casting is by abrasive blasting (either grit-blasting or a combination of grit and shot). Cleaning is traditionally performed at the foundry before shipment to the galvanizer. However, some galvanizers are able to perform abrasive blasting at their facilities - check with your galvanizer before sending your parts.
Sound, stress-free castings with good surface finishes will produce high-quality galvanized coatings. The following design and preparation rules should be applied for castings to be galvanized:
· Avoid sharp corners and deep recesses
· Use large pattern numerals and generous radii to facilitate abrasive cleaning
· Specify uniform wall sections. Non-uniform wall thickness in certain casting designs may lead to distortion and/or cracking. Cracking results from stress developed as the temperature of the casting is increased during galvanizing. Uniform wall sections and a balanced design lowers stress.
As always, if you have any questions regarding this or any other galvanizing topic, please don't hesitate to contact us:
Tuesday, February 26, 2013
Why do some fabricated assemblies distort during galvanizing?
Stresses induced during steel production and in subsequent fabricating operations, are sometimes relieved when exposed to the high temperature of the molten zinc in the galvanizing kettle (generally around 840 deg. F). Also, parts of dissimilar thicknesses that are welded together can expand and contract at differing rates, based upon their thickness. When one of these materials tries to expand or contract and the other material is stationary, distortion can occur. Galvanizing these types of materials separately can be of great benefit to the manufacturer, from a distortion control standpoint. For example, with a channel frame and thin plate assembly, the frame and plate should be galvanized separately and bolted or welded together later, rather than welded together before galvanizing.
Guidelines for minimizing distortion and warpage are provided in ASTM A384,Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies, and CSA Specification G 164, Hot Dip Galvanizing of Irregularly Shaped Articles.
Tips for Minimizing Distortion
To minimize changes to shape and/or alignment, design engineers should observe the following recommendations:
-Where possible, use symmetrically rolled sections in preference to angle or channel frames.
I-beams are preferred to angles or channels.
-Use parts in assemblies that are of equal or near equal thickness, especially at joints (Figure 5).
-Use temporary bracing or reinforcing on thin-walled and asymmetrical designs (Figure 6).
-Bend members to the largest acceptable radii to minimize local stress concentration.
-Accurately preform members of an assembly so it is not necessary to force, spring, or bend them into position during joining.
-Continuously weld joints using balanced welding techniques to reduce uneven thermal stresses. Pinholes from welding are very dangerous in items to be galvanized and must be avoided. Staggered welding techniques to produce a structural weld are acceptable. For staggered welding of 1/8-inch(4 mm) or lighter material, weld centers should be closer than 4 inches (10 cm).
-Avoid designs that require progressive-dip galvanizing. It is preferable to build assemblies and sub-assemblies in suitable modules, so they can be immersed quickly and galvanized in a single dip. In this way, the entire fabrication can expand and contract uniformly. Where progressive-dip galvanizing is required, consult your galvanizer.
The last tip brings about a great point - if you have any questions regarding proper fabrication techniques to facilitate galvanizing, ALWAYS contact your galvanizer! At Hubbell Galvanizing, we are happy to assist you with any questions you may have. Feel free to contact us at the following:
(800) 244-4258 - Toll-free
(315) 736-8311 - Office
(315) 736-0381 - Fax