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The purpose of galvanizing (zinc coating) is to slowdown corrosion (rusting) of plain steel.

Durability in terms of retarding the onset of rust is many many times that of ungalvanized steel.

Safety cannot be evaluated without more information on the application.

Same with performance factors- what is the application? What grade of steel? What is its form?

Our ability to give good answers is determined by the quality of the questions.

milo

The performance factors are dependent upon the conditions of use:

1. Applications - Is it for roofing or storage tanks or durable white goods or other appliactions.

2. The contents inside the storage vessel going to be - Is it raw or treated water or some other solutions. Whether treated water stiil has some low level of alkalinity or acidity.

3. What is the coating thickness on the basic steel sheet and what is the thickness of base sheet?

4. The life of coating thickness depends on factors (2) and (3) above. Also on the severity of usage or external abrasions or damages to the zinc coating.

5. The purpose of galvanising is to protect mild steel sheets or plates from corrosion.

S.K. PRUTHEE

The purpose is extracted from its name -galvanised- to prevent the formation of galvanic cells at surface of steel, and you know the effect. For safety in dealing with galvanized surfaces, don't weld these surfaces where the fumes from heated elements used in galvanizing are very harmful to human.

nice post Abdel Halim Galala!

Nice approach by showing the meaning of the meaning of the term involved.

Education without pain!

milo

Abdel is right (as usual) about the fumes being dangerous to breathe. Coming up in industrial welding I always heard about "galvanize poisoning" and so when ever I had to weld or cut something that was galvanized I would try to get some sort of ventilation going. A few years back while I was managing a start-up on a large piping job I decided (out of boredom mainly) to start installing toe plates around pipe floor penetrations in the galvanized grating. I thought that I had enough ventilation at the time but I found out later that I was wrong. I had uncontrollable chills, headache, nausea for about 6-8 hours that night and it took me 3 days to really get to feeling to where I could eat. I have heard that once you get galvanize poisoning that it builds up in your system and makes you more susceptible to get it again. I don't know if this is true but if I as much as smell it today it makes me feel nauseated. When steel is hot dipped it does have somewhat of a negative effect on the strength. Once mild steel is galvanized you can not heat it and bend it like you would normally without it cracking. Even if you grind off the galvanize coating it will crack when you try to bend it. Not sure why this happens but I have seen it more than once first hand. I was making brackets once from 3"x3"x3/8" galvanized angle iron where I was planning on cutting a 45 degree notch and heating and bending it to make a 90 degree knee bracket. After cutting and grinding up about 25 or so of these brackets I started to heat and bend them and every one of them would crack. I learned my lesson from this and from then on I make the brackets from plain mild steel and then send them to be hot dipped. Does any of you metallurgist guys out there know what causes this?

pipewelder

Thank you pipewelder and thank you Milo,

The following statement is extracted from a site to declare the dangerous of zinc particles: "Did you know that you can "contaminate" your family by bringing home zinc particles on your clothing? Protect both yourself and your family-weld safely"

The following are samples of sites that are interesting in welding after hot dip HDG galvanizing and its precautions:

1. [PDF] Welding Galvanized Steel -- Safely

2. 13244. Zinc or Galvanized Poisoning Symptoms

3. 8535. WELDING FUMES FROM GALVANIZED METAL

4. Welding Galvanized Sheet

Please Protect both yourself and your family-weld safely.

The last point that is very important to deal with welding after HDG is the cost of re-galvanizing of portions that were welded after HDG is significance, otherwise these portions will be corroded rapidly, since the portions are not protected in addition to locating the case of two dissimilar metals.

For that reason, in galvanized piping systems such as in fire fighting and cooling networks, we do our best as a designers to make a good and complete design drawings, no way to miss any fitting (even a small half coupling for a sprinkler) and no way to any dimension mistakes. And a complete HDG is carried out after good design, good fabrication, and pass hydrotest.