Question-Answer for Degree of Galvanizing

8/6/2019 Question-Answer for Degree of Galvanizing

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Question on Hot Dip Galvanising

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In hot dip galvanising, why we use, lower layer of lead along with Zinc with other metalcomposition in metal pot and what is the basic function of lead in hot dip galvanising.

Vipin Jain

galvanised steel manufacturing - Biratnagar, Morang, Nepal

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Hot-dip Galvanizing is based on alloying Iron with zinc. Traces of iron introduced into the zinckettle(carry-over with the material to be galvanized from wet pre-treatment, from the steel zinc-kettle-wall and the material to be galvanized will alloy with the zinc too, thus forming zinc-ironalloy particles called dross. This dross is some heavier than the zinc and will slightly sink tobottom of the kettle. Lead has two functions: 1. dissolved lead in the zinc-melt has influence onthe fluidity of the zinc and will help dross particles sink to the bottom - floating dross particles
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will cause roughness on the material to be galvanized(bad quality) 2. The lead layer on thebottom of the kettle will prevent dross will be stuck to the iron kettle-bottom and makes itpossible to remove the dross from the bottom of the kettle, because lead is heavier than the drossand will not alloy with the dross and zinc - so dross floats on the lead-layer.

Dolf van den Berg

- Leusden, The Netherlands

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In my previous question, I asked, why we use lower layer of lead in zinc kettle, I got satisfactoryanswer. Now will anyone please tell me, can we use another metal in place of lead in zinc kettlefor such functionality in galvanising process.

Regards,

Vipin Jain

galvanised steel manufacturing - Biratnagar, Morang, Nepal

+++Coming back on your second question I don't know the reason why you like to change lead forsomething else, but in Scandinavia lead will be forbidden for environmental reasons.

Bismuth or Tin could be elements to replace the function of dissolved lead. These elementscause a high fluidity of the zinc and a good wetting of the steel. De-drossing of the kettle ishardly a problem. Cominco - Canada made investigations adding Bismuth to Zinc for hot-dipgalvanizing.

Regards,

Dolf van den Berg

- Leusden, The Netherlands

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Regarding to the question of dross forming, how to minimize the dross forming? Is the


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temperature of the zinc bath influence the dross formation? Or should we put some additiveelement like aluminium to minimize?

Catherine Sim Li Ling- Kuching, Sarawak, Malaysia

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Temperature has influence on dross forming (the higher the more iron loss), but with normalgalvanizing temperatures (around 450 degr.C) there is hardly no difference. At a temperature490-520 degr.C your kettle is in danger (high iron loss. Aluminium makes zinc more fluid,influences the structure of the alloy layer, reduces zinc-ash forming and gives a better color andgloss of galvanized material. Biggest influence on dross forming is carry over of dissolved ironfrom pickling via rinse and flux. Finally I have to tell you the whole process is too complicatedto explain everything via finishing.com. Maybe you need a galvanizing course.

Dolf van den Berg- Leusden, The Netherlands

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Aluminium have the function in cleaning oil of cold roll steel sheets. Anyone can rectified thisstatement? If true, how is the process?

FY Fong

- Malaysia

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Which of the parameters responsible for dross generation and how to reduce top and bottomdross? actually I'm doing thesis on reduction of dross generation . So I want to know theparameter on which the dross generation depends and also how to reduce the dross generation ?please give the response as soon as possible.

Bharat Kumar Lautre

SLIET COLLEGE OF ENGG - PUNJAB, INDIA

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Dear Mr LAUTREPlease write Title of your project, & faculty you belong. In research You have to carry out lot ofliterature survey. & potentiality of investigation has to be ascertained. Hearing from you I mayprovide little clue & rest is your dedication

BEST WISHES,

Dr Pradeep kumar Maitra


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- BHILAI, Chhattisgarh, INDIA

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SIR-I WANT TO KNOW - HOW TO REFINE THE LEAD FROM THE BOTTOM LAYER OFLEAD USED IN HOT DIP GALVANISING TANK I.E ZINC BASED LEAD, CONTAINSDROSS ALSO ? AND WHAT WILL BE THE RECOVERY EFFICIENCY ?

GULSHAN RAM

- HYDERABAD, INDIA

September 25, 2008

Hello Sir,

I have seen earlier question & answer for earlier question, its very impressive.

I need some clarification.1. Regarding CoatingWe are repeatedly facing problem in galvanizing hardened & tempered low alloy steel. Coatingwill not be uniform, un galvanized patches & all, but in case of mild steel there is no suchproblem, what shall be the reason.

Also if the material is having grinding finish, is galvanizing coating makes any difference.

2. what's the roll of flux in galvanizing & what's the correct fluxing method & how to make &use flux.

Hope you will do the needful at the earliest.

Thanks & Regards

Prashanth

PRASHANTH- INDIA

August 3, 2009

How to minimize dross formation?

Sami Allen- Saudi Arabia

August 21, 2009

Hi, Cousin Sami. Mr. Van den Berg has invested a bit of his time answering that question. In theinterest of not starting over, and to show thankfulness for his effort, please try your best toexpress your question in terms of what has already been said. Thanks!
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Regards,

Ted Mooney, P.E.finishing.comBrick, New Jersey

September 13, 2009

DEAR SIR,

IN HOT DIP GALVANIZING, PURE LEAD CHARGES IN POT FOR SAVE THE LIFE OFPOT, LEAD BEHAVE AS A CUSHION EFFECT.

rajkumar singh

- bombay, India

October 19, 2010

So what would be the ideal amount of Lead to charge in a Zinc bath (lead layer thickness or %zinc)?

Jaydip Atodaria- Harare, Zimbabwe

October 19, 2010

Hi, Jaydip. Some people think the ideal amount is zero :-)

You can search the site for "lead-free" galvanizing. Good luck.

Regards,

Ted Mooney, P.E.

finishing.comBrick, New Jersey

October 26, 2010

Dear Sir,

Thanks for your reply. Our problem is we have a zinc tank 10x1.0x1.5m deep which leaked and


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we are in the process of changing the kettle. From the pot wear it seems it weared out due todross. Will adding a layer of lead increase the effectiveness of drossing? Then in that case weneed to know when charging the new bath how much lead should be added?Thanking you.

Jaydip Atodaria

- Harare, Zimbabwe

October 26, 2010

Sorry Jaydip, I can't answer that. You can wait for someone more experienced in this area tostumble across your inquiry, or you can patiently search the site because similar subjects havebeen discussed at length by true experts several times. Good luck.

Regards,

Ted Mooney, P.E.finishing.comBrick, New Jersey
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Question-Answer for Degree of Galvanizing

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