Hot-Dip Galvanizing Kettles: how to build or where to buy

A. It is indeed an interesting idea. But a kettle is a wearing item, it slowly dissolves in the zinc. Putting a thinner lining on the inside would require that the lining itself does not also dissolve, otherwise after the lining is dissolved, the lower grade steel behind it would rapidly deplete.

So the question really is what rate does some other alloy such as "stainless" dissolve. You mentioned a family of steels with widely variable chemistry. The more common forms of Stainless, 316, 304 etc would not be suitable, their rate of dissolving is slightly slower than low Si carbon steel, but not that much. Someone might know about special grades such as duplex, where the Fe content is low or nil. That might be the area to look at.

Cost is always a consideration too. I could imagine a duplex steel kettle being very expensive.

A. In the United States it called Flange and Firebox quality steel. It basically is a very low carbon, very low silicon steel plate. Rods for welding it should also be low in C and Si.

A. Dear Sir:
About 35 years ago kettle makers used "max ten" which means that the kettle "steel" was nearly pure iron with the combined alloying agents adding up to less than 0.10%. Armco made "steel" (iron) of this type. Today I do not think this type steel is available. Another term that I have heard is "boiler plate steel."
Today there are two kettle makers that likely make most of the galvanizing kettles. One is in the USA and the other is in Germany. These kettles now usually have 2 inch thick walls (years ago they were 1 inch thick). The weld rod and welding methods are quite specialized. I recommend that you purchase rather than make a kettle. With a proper kettle and proper furnace, the kettle can last 10 or more years. A poor kettle and poor furnace can give a kettle life of only a few months.
In the journal Metal Finishing you can get my article on kettle furnace design though interlibrary loan (xerox copy) from most large libraries. This article details the most efficient system which is end-firing with high velocity burners. Galvanizing kettles and galvanizing kettle furnaces are NOT do-it-yourself projects.
Regards,

A. The most critical element in the steel for kettles is Silicon.
This needs to be at or close to zero.
Silicon is used extensively in steelmaking to de-oxidize the steel while molten and in casting processes. (The slabs cast in continuous casting plants are later rolled to plate.)

Alternative de-oxidants are available for this special grade of plate.
S and P are also important.

A. Hi Asit. Welcome! We appended your inquiry to a thread which answers some of your questions, but it's a tall order to ask for complete instructions for safely designing and fabricating a galvanizing tank. I don't think it's going to happen for free in a public forum.

Good luck, but if you don't have all the info you need quickly enough, please see the ads for galvanizing consultants at the bottom of the page.

Regards,

A. You should not attempt to make a galvanizing tank yourself if you cannot answer these questions.

Your depth of 0.5 m seems far too small. What could you use such a tank for?

At length 5.5 m, more typical dimensions would be 1.2 m wide and 2-4 m deep. Material will be very low Si steel, a special steel not readily available, and made especially for this purpose of galvanizing tanks. Typically its 50 mm thick. Special welding electrodes are required, and special techniques for welding.
There are 3-4 suppliers worldwide who supply long lasting kettles, but the furnace is equally important for long life.
You might expect 10 years or more from a well made kettle of the right material.
You might expect a few months from a homemade one.

A. Hi, Asit.

Its better to define first size of your materials which are going to be galvanize and required production per day or per shift.

Based on same you have to select the size of your Galvanizing kettle.

A. Dear Ruphert Connok.

It's better to hire a consultant and supplier who can guide you how to start Galvanizing plant. It will be more advisable then doing it yourself.

Thanks.

A. Not a good idea to build your own kettle for galvanizing if you have to ask how to do it.

If you want it to last any time, then buy one from a reputable supplier. There are several, even one not so far from you.

Homemade might last 6 months. Bought one 10-14 years.

? Hi Teslime. We appended your inquiry to one of several threads here on galvanizing tank construction. I'm reading between the lines that you are talking about a tiny kettle for a short-term experiment, but if you can give us a feel for its size it might be helpful.

Regards,

A. Several steel manufacturers make a special steel for this application. It's a low carbon mild steel, but with ultra low Si - almost zero. I'm not sure if there's a grade name.
To make a kettle out of plain grades of steel would be to ensure a very short life for the kettle.

A. Dear Sir.

It's better to purchase Kettle from Reputed manufacturer as they have experience in manufacturing kettles.

Steel generally used to manufacture Kettle should be low carbon, low silicon, with same property for welding electrodes.

A. Dear Aleksandro Bardhi,

Selection of Metallic or Ceramic bath mostly based on what kind of materials you would like to Galvanize.

Generally for Fasteners, threaded items peoples are going with Ceramic bath with higher temperature otherwise for structure and bigger job, better to go with Metallic bath.

A. Dear Sai.

Basic reason of deterioration in Galvanizing pot are

1 ) uneven heating
2 ) furnace design.
3 ) Deposition of Hard zinc (Dross) inside zinc kettle.
4 ) Quality of Pot materials.

A. The best material for kettles is "CLASS A DSQ (Dead Soft Quality)" and "GP2"

Warm Regards,

A. Dear Marcin.

According to your subject, it looks like you would like to start small Hot dip Galvanizing plant.
first of all we need to know what kind of materials that you are going to be Galvanize, what would be size of materials and what amount of quantity you would like to produce per day in 8 hrs. shift.

Based on all above , we would suggest you more on size of Kettle and its feasibilities.

? Dear Sir.

You mean to say , you would like to galvanize 12" dia pipe and length of pipe would be 6'-0" long and you would like to dip it vertically.

At a time how many pipes you would like to dip or per day how many pipes you would like to Galvanize.

Based on your answer we will revert back with suitable size for your product.

adv.
You may contact us directly on sales@gunatit.com

A. Hi Ilesh. No, I think Marcin is proposing that his galvanizing kettle will be a 12" diameter pipe standing about 6' tall, with a bottom plate welded onto it, and the weld protected from the zinc by powdered ceramic insulator material.

I think, however, that 12" diameter pipe is seam-welded rather than cast or extruded. So if the zinc preferentially attacks weld lines, this would still be an issue.

If you get a chance, look at Marcin's fascinating "TED Talk". His interest is in deploying small, simple, inexpensive machines around the world as the building blocks of civilization.

Luck & Regards,

A. Hi Basel. Yes there is a risk. Please see Dr. Thomas Cook's comment on this subject on thread 57908

Luck & Regards,

A. Yes there's some risk.
A kettle should not be overheated locally, but requires the temperature of the steel to be as even as possible. If it reaches about 500 °C, then serious erosion of the kettle wall occurs. This is the kettle dissolving in the zinc. Its fastest rate is somewhere around 530 °C, but anything over about 480 °C is too fast. This thinning of the kettle wall keeps going wherever zinc is touching the wall on the inside.
If the zinc level is low, then the top layer of zinc is touching, however low that might be. A furnace is designed to have an unheated area at the top, perhaps about 20 cm from the lip downwards, and it's for this reason. Heat is then only applied to the area that is internally submerged in zinc, so the heat flows into the zinc and doesn't cause the steel to overheat. If you let the level fall too low, below the insulated unheated area, then the steel of the kettle will overheat.