Hot dip galvanized 1

[Ciaci]

Hi guys,
I have to follow a piping project specification that requires A 106 Gr pipes. If the pipe has to be hot dip galvanized for process reasons, does this means consequently that the pipe has to follow
the ASTM A 153?
Does it means consequently that fittings and flanges have to be hot dip galvanized too (and consequently have to follow the ASTM A 153)?

Other questions:
Maybe it is only a language issue, what is the difference between zinc coated and hot dip galvanized?

Thanks in advance

 

[bimr]

Yes, ASTM A153 / A153M - 09 is the Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Piping.

Electrogalvanized is just another term for zinc electroplated. That means the steel is immersed in an aqueous bath, and electricity is used to move electrons from the anode to the cathode, which induces the zinc anodes to be oxidized and dissolve as zinc ions in the aqueous solution, be transported as ions through the solution, and be reduced as metal onto the work (the cathode).

In hot dip galvanizing the work is immersed in molten zinc. As it is withdrawn, the zinc cools and forms a coating of zinc on the work.

Hot dip galvanized coatings are almost always several times thicker and therefore several times as corrosion resistant. There are some other practical differences in the two coatings for different applications as well.

Galvanizing is a favored method of protective coating due to its low cost, ease of application, and long maintenance-free service life. It is the most common outdoor protective coating in use. When used on bolts, due to the thickness of the zinc coating, all galvanized nuts must be tapped oversize.

Zinc plating or electroplating is a process where zinc is applied by using a current of electricity. It is a thinner coating than hot dip galvanizing making it unsuitable for outdoor applications. Its advantages are its brightness and uniform color making it more aesthetically appealing.

http://www.piping-engineering.com/piping-hot-dip-electro-galvanization.html

 

[Ciaci]

Thanks bimr. Are these process applied inside the pipes as well?

 

[bimr]

Yes. One problem with galvanized pipe is when the pipe is threaded, the galvanizing is removed where the pipe is threaded. The other problem is the coating is removed if the galvanized pipe is welded.