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"Peeling of zinc in continuous hot dip galvanizing processes"

Current question:

October 24, 2021

Q. We producing GI wire of sizes from 2.60mm to 3.90 mm. We facing problem on zinc coating, when we make gabion box or making springs for gabion box coating on wire is cracked how can we get proper coating please suggest us
Carbon content in ms wire is 1008.
Thank you,
Elite wires pvt. Ltd.

Nurlah Ansari
- Hetauda, Nepal

October 2021

A. Hi Nurlah. May we assume that you mean hot dip galvanized wire, not electrogalvanized (zinc electroplated)? In either case, can you give us the thickness of the zinc, and the galvanizing or electroplating specification if any? Carbon content is '1008' -- that means 0.1008% carbon, not type 1008 steel? Finally, is this process something that you have been doing for a long time and this problem suddenly came up, or is this a startup operation and you have not yet achieved success? If so, have you tried buying a bit of a competitor's wire and forming it for your gabion boxes and springs? Can we get photos to better understand what you mean by cracking? Thanks!

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Closely related Q&A's, oldest first:


Q. We are manufacturer of Chain link Fencing from Galvanized wire. During the course of forming of wire, zinc peels off from the bend, can you suggest a means to overcome the peeling of zinc.

Mohammadi Daud
- Karachi, PAKISTAN


A. Hi, Mohammadi. It is hard to be specific from this distance and with limited information, but it sounds like the wire may not have been properly cleaned and fluxed. Give us more data if you can please, and read the other comments here for food for thought.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


Q. We face problem of Zinc coating peeling in hot dip anodizing of Cable Armour wire. If we increase the Silicon content to improve the adhesion, the resistivity of the wire goes higher than specified. Hence we have to use Silicon lower than 0.05 %. Is there any other way to improve Adhesion of Zinc Coating ?

Sudhir Joshi
Tata Iron and Steel Co. - Mumbai, Maharashtra, India


Q. We face a problem of zinc peeling in our CGL (continuous galvanizing line) hot dip with non oxidizing vertical furnace and horizontal radiant tube furnace. We checked the O2 ppm in the radiant tube furnace it was 5 ppm; checked the pot composition and it was ideal. We checked the furnace for leaking, it was not leaking. Anyone have any idea for the reasons?

Ahmed Milad
Sr. maintenance engineer - Egypt


A. I can think of several reasons that could possibly cause the zinc to flake off. More information may be needed to help diagnose your particular problem. Without knowing how severe the adhesion problem is, or if it is flaking off while it is in the line, or during the adhesion test, some ideas could be:

1. Improper cleaning prior to the furnace could be a cause, especially if the strip is oily. More heat in the direct fired section could help in this area.
2. The atmosphere in the furnace could need adjusted (more hydrogen possibly).
3. The strip temperature going into the bath could be too low.

Mark Popielski
- Terre Haute, Indiana, USA

December 12, 2011

A. There can be several reasons for the peeling. It's all hit and trial method to reach at the root cause. But you need to analyse the samples first. Put the sample into 30% HCl solution for a minute or two to check the surface under coating.
1. If you see under surface bright and white enough after removing the Zinc coating it means the strip is not oxidized and ok for coating in this condition; you need to put attention on pot bath chemistry and CRC composition. May be silicon and carbon more in your CRC.
2. If you see the under surface black after removing the zinc coat it means you need to attend the furnace parameters. The strip is getting oxidized before coating which is like a cancer for the galvanizing.
a. First thing is to check all manholes gaskets and sealing using leak detector; please check the cleaning of strip.
b. Check for furnace leakages.
c. Pressure testing needed for all zones of furnace.
d. Check for any water leakages (hearth rolls, jet cooling blowers, water cooled damper, entry seal jackets).
e. Your dew point in furnace will indicate the water presence.
f. Check the Nitrogen & Hydrogen dew point and purity (PPM).
g. Need to check the flames of direct fired zones (try to adjust the air/fuel ratio depending upon your fuel whether CNG or LPG).
h. Take trial by running at low air/fuel ratio.
i. Sometimes snout shoe may have leakage which is hardly visible, so take the trial by running the line at high zinc bath level and see the result (if no peeling at high bath level and peeling starts at low bath level it means certainly your snout shoe leaking).
j. At extreme condition you need to do pressure testing of radiant tubes and heat exchangers.
k. High zinc coating also leads to adherence problem.
l. Aluminium % also needs to be checked.

Sujit Kumar
- Bokaro Steel City, India

Snout Leakage in Galvanizing

November 20, 2013

Q. Dear Experts
Snout is one of the most important parts in Hot-Dip galvanizing.
So we have to control the situation of the atmosphere during process.
However, sometimes because of leakage, the atmosphere becomes out of control.
Now, if you let me I would like to ask you:
1-Have you ever had any experiences about Snout leakage?
2-How could you realize the Snout leakage?
3-How does this problem affect the quality of your products (specially about black spot)?
4-And finally, how could you resolve this problem?

Ehsan Parshizfard
- Iran

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)


Q. I am process engineer responsible for continuous galvanizing line, we have great problem of peeling on our galvanized products , what are the different variables we should check to discover the reason of this defect , what are the effect of different impurities element on the zinc path on peeling and what are their limits .

Mohamed Farag Attia
Kandil Steel Company - 10th of ramadan, Cairo, Egypt


thumbs up sign Sir:
If your line is a flux line it is possible that I could help. If it is not, I do not have sufficient experience in gas lines to be of value to you.

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA

Zinc peeling observed in zero spangle bath


Q. I am Pramod Kumar Sinha a Process Engineer in Continuous Galvanizing Line in Cairo /Egypt. I am facing zinc peeling problem in new galvanizing line.

When we create new bath of zero spangle (Pb-0.005%) after galvanizing we face peeling above 140 gsm coating. But when we change the bath with normal spangle (old prepared & used from 6 month) we face no problem and found good adherence up to 360 gsm. I am not getting what is the reason behind it. Details of bath analysis is like this:

Al       Fe       Pb     Result           Remarks

0.63     0.04     0.005  Poor             New bath
                         adherence        prepared

0.52     0.013    0.011  Poor             Ditto

0.453    0.011    0.006  Poor             Ditto

0.292    0.012    0.003  Poor             Ditto

0.24     0.012    0.003  Poor             Ditto

0.22     0.007    0.054  Ok at 360 GSM    Bath change
                         and continuous   from zero to
                         in all coating   normal spangle

Pramod Kumar Sinha
- 10th of Ramadan , Cairo, Egypt


A. Hi
I think too much Al% in zinc pot will reduce adherence you have to pay attention to your speed it means the remaining time in zinc pot

Jamal Ashoori
msco - Isfahan, Iran

2006 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. What are the characteristics/bath composition which define/differentiate zero and normal spangle bath?

Atul Mishra
ERW pipes - Maharashtra, India

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)

How to overcome zinc peel off in Galvanizing?


Q. We are facing a problem of zinc peel off in continuous galvanizing line. It is not a continuous one but occurs sometimes. Still we are unable to find the root cause, please help me to overcome this problem permanently.

Plating shop employee - Mumbai, Maharashtra, India


A. Hi
I think in this line [it is common to have] peeling; pay attention to your cleaning condition and Al% in zinc pot.

Jamal Ashoori
- Isfahan, Iran

To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)

Peeling problems in Hot Dip continuous galvanizing Non-Ox furnace


Q. Dear Sir,

We have serious peeling problems in our plant. We had been suggested that the main reason is leakages; we have plugged all leakages. The ratio of fuel to air is also a recommended oxidising in the first 2 zones and reducing in the other 2 zones.

The plant was working good with zero spangle but after we changed the zinc bath for minimum spangle the problem of peeling resurfaced.

We have checked all leakages and it has been arrested; the percentage of Al is 0.20 to 0.26%.

Now please, if any person can help us in solving the problem.

What can be the possible cause of peeling after change over of Zinc bath from zero to minimum spangle?

As we were getting 350 gm/m2 with zero spangle and after changing the zinc bath, there was peeling from minimum thickness also .

The bath chemistry was found to be with in the standard prescribed requirement.

We do galvanizing of FH and HR coils, The coating is 90 gm/m2 to 350 gm/m2.

The thickness range is from 0.18 to 1.5 mm.

Dilipkumar Singh
steel complex - Cairo, Egypt


A. Without giving the details on what you did during change over of Zinc bath (or) what was the real change during mini spangle to zero spangle, it is difficult to fix the problem.The problem may be with oil in CR coil or with furnace temperature too.

- Chittagong, Bangladesh


Q. We have not done any change in the Pot , we have 2 different pots for Regular and zero spangle, and I would like to bring to your notice after I changed the Pot the zinc peeling problem disappeared.

Dilipkumar Singh [returning]
- Cairo

May 30, 2008

A. Composition of zinc and its alloys may be changed. Go through leakages, furnace parameters, N2H2 gas quality, etc to be analysed.

G Nataraju
- India

September 19, 2008

A. Please check the oil in CR coil; if oil contaminant is high then keep more temperature in first two zones. Check the dew point in furnace, increase aluminium % up to 0.30, check the pressure of lpg and air and its ratio.

- Nagpur,M.S. India

July 19, 2014

A. I understand that you have two zinc baths ... let me know the pot equipment details, i.e., roll dia. & center distance of roll at X & Y axis ... furnace & other process section is okay.
Just you have to focus on bathe chemistry and pot equipment, i.e., roll sizes, etc.


SA Hashmi
- Guwhatati Inida

Is lead content the cause of lack of adhesion in continuous galvanizing?

February 27, 2014

Q. Is lead the culprit for delayed adhesion failure in continuous galvanizing? We use 0.08 max. in Zinc bath. Commercial quality coil shows failure in adhesion during forming.
Seen SEM structures, inter spanugular opening observed in skinpassed material.


Galvanized coating is peeling off of wire

September 16, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear Sir,
We are having a problem about galvanized steel wire in 1.80 mm diameter. Wire is used for C-ring production and packed in 500 kg spool. One spool has no problem but on other spool coating is peeling. Both spool wires produced at the same time in same conditions. Zinc sticks on the part of machine.


Thank you


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