Galvalume (Aluminum-Zinc coated) C-Purlins Weldability

[lager]

There are conflicting information in the net about the weldability of galvalume (aluminum-zinc coated) products like C-purlins (1.5mm thickeness). I'd like information about their weldability from actual hand-ons or knowledge.


For a 1.5mm galvalume coated C-purlin.. What is the thickness of the coating? Thank you.

 

[thaidavid40]

From what I have seen personally, galvalume sheet can be welded, but you have to crank up the welding machine to overcome the coating's resistance (or else ground the machine to an area where the coating has been ground away). Not everybody can weld thin sheet at these relatively higher amperages. It takes some uncommon skill, so find you a good, skilled welder.
Good luck,
Dave

Thaidavid

 

[kingnero]

and those weldors don't live long, due to the zinc fumes.

 

[lager]

What is the difference in appearance between galvalume purlins and galvanized purlins? Can galvalume be made into 1.5mm thickness producing C-purlins?

 

[ajh1]

AS thaidavid40 points out, welding on either galvalume or galvanized material, particularly thin gauge, requires a very knowledgeable welder. In the US, the qualification practices are per AWS D1.3. Proper safety precautions in terms of ventilation are mandatory for either. In addition to the zinc fumes, a lot of both kinds of material are coated with an acrylic coating that may contain hexavalent chromium when heated. This creates a slippery surface so that forming oils are not required for the roll-forming process which eliminates a lot of potential pollutants in the manufacturing stream as well as eliminating oil on panel surfaces. Galvalume is primarily seen on panel thicknesses, i.e., 22, 24 26, or 28 ga., but I don't know of any reason it couldn't be put on a purlin coil.

 

[lager]

I also read that galvalume can't be used with concrete, mortal or cement board.. the application of the purlins would be supporting cement board.. the reason being it has to do with the alkaline nature of these reacting with the aluminum. Supposed the galvalume purlins support cement board.. would the part that corrode only the aluminum-zinc coating making the coating vanish or will it eat thru the bare steel inside even if it's not wet? Are corrosion contagious enough to infect the whole material inside even without the presence of water?

 

[lager]

AS thaidavid40 points out, welding on either galvalume or galvanized material, particularly thin gauge, requires a very knowledgeable welder. In the US, the qualification practices are per AWS D1.3. Proper safety precautions in terms of ventilation are mandatory for either. In addition to the zinc fumes, a lot of both kinds of material are coated with an acrylic coating that may contain hexavalent chromium when heated. This creates a slippery surface so that forming oils are not required for the roll-forming process which eliminates a lot of potential pollutants in the manufacturing stream as well as eliminating oil on panel surfaces. Galvalume is primarily seen on panel thicknesses, i.e., 22, 24 26, or 28 ga., but I don't know of any reason it couldn't be put on a purlin coil.

For 1.5mm that is not thin gauge.. does it still requires very knowledgeable welder.
Can one also sandpaper away the zincs before applying welding.. in appearance, how exactly can you the difference between the two (see my comment on previous message to this too)

 

[lager]

Thanks for the tips that it takes higher current to weld galvanized steel... we just returned all delivery of the galvanized purlins and ordered bare steel.

I need to know something. What is the effect of rust primer on the bare steel in welding? Does it have the same effect of needing higher current.. this is for both red oxide rust primer and epoxy primer. Should steel be primered only after they are soldered? Thank you for all the assistance.

 

[ajh1]

Thin gage for the purposes of the welding codes is anything less than 0.188" thick. Between 0.125" and 0.188" you get to pick whether to follow the AWS D1.1 plate welding code or the AWS D1.3 sheet welding code.