After galvanizing, the continuous zinc coating is physically wiped using air knives to produce a uniform coating across the width of the strip. The uniform coating consists almost entirely of unalloyed zinc and has sufficient ductility to withstand deep drawing or bending without damage. A variety of coating weights and types are available, ranging up to just over 3 mils (76 µm) per side. One of the most common zinc coatings is Class G90, which has 0.9 oz/ft2 of zinc (total both sides) or about 0.80 mils (20 µm) thickness per side. Continuous sheet galvanized coatings often get confused with batch hot-dip galvanized coatings because the term “galvanizing” is used interchangeably. The table below compares the available coating grades of continuous and batch hot-dip galvanizing and their corresponding coating thicknesses. Zinc coating thickness is proportional to the service life as evidenced in the Time to First Maintenance Chart. Continuously galvanized sheet steels are used to make cars, appliances, corrugated roofing and siding, and culvert pipe. The coated product can be suitably treated for painting, which will increase the service life. Because of the thin coating, this product normally is used for interior applications or where exposure to corrosive elements is mild.

See Also: Zinc Coatings Publication

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Comments

Alana Hochstein

Hi Geon Woo Park,

For dry ammonia gas, galvanized steel performs well with no excessive heat or moisture.  You may see an additional corrosion rate of approximately 5 ┬Ám / year (0.197 mil / year).  However, the presence of any chloride with the ammonia gas will increase this corrosion rate. 

Galvanized steel has been used successfully in fertilizer plants with dry ammonia in the environment.  One such plant (Joffre Nitrogen Operations in Joffre, Alberta) has the majority of its steel structures hot-dip galvanized. Construction was completed in 1987 and the current condition of the galvanized structures are excellent.

For wet ammonia gas, galvanized steel also performs well except for pH levels 12.5 and above.  However, factors such as agitation, aeration, temperature, polarization, and the presence of inhibitors also may change the corrosion rate.

We do not have any corrosion information at this specific concentration of 200ppm.

Geon Woo Park

I visited your web site. We are Hyosung Coporation, Power & Industrial System R&D Center in Seoul, Korea.

My name is Geon-woo Park, Core Technology 2 Team.

We are trying to install the system in India this year. Our system used a product hot-dip galvanizing.

Unfortunately, atmospheric environment of the installation site includes the ammonia gas 200ppm.

We request the corrosion data of the hot-dip galvanized by the ammonia gas concentration.

Please let us know if you can provide the our request.

We look forward to hearing from you.

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