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topic 49676

How to calculate/measure the thickness of zinc coatings

A discussion started in 2008 but continuing through 2020

August 14, 2008

Q. I would like to know what will be the thickness of the electroplating in microns, on MS sheets of flats, when 610 gms/sqmt of zinc is used.

Vinod Kumar
Design engineer - India

August , 2008

A. Hi, Vinod. Usually electroplating is expressed in thickness but phosphatizing is expressed in weight because the meaning and usefulness of the term 'thickness' becomes compromised when you are speaking of a conversion coating which includes some dissolution of the original substrate, transition areas, various different compounds, and a spikey surface.

But if this is zinc electroplating and the density of zinc metal is about 7.14 g/cm3, then you have 610/7.14 = 85.4 cm3 or .0000854 m3 of zinc spread across 1 m2.

So the thickness is .0000854 meters or 85.4 microns or 3.3 thousandths of an inch. That would be too thick for zinc electroplating and sounds more like galvanizing. Typically, and per spec, zinc electroplating would be 5, 8, 13, or 25 microns thick based on whether the service condition was mild, moderate, severe, or very severe.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

August 15, 2008

A. 610 g/m2 is the often used equivalent of 85 microns used for hot dip galvanizing.

Can't imagine electroplating that thick!

Geoff Crowley
Geoff Crowley
Highland Galvanizers - Glasgow, Scotland

Calculating the cost of too-thick galvanizing

May 7, 2017

Q. I am galvanizing steel structures. The zinc micron thickness is higher than the standard coating. For example, I need 85 micron for steel whose weight is 10 ton and I am getting 100 microns for the same weight after checking by Elcometer. The difference of the microns is losing me money, so I need to calculate how much grams I am losing because of the difference of the microns.

john picol
- uae

May 2017

A. Hi John. If you multiply the thickness of the coating (100 microns) by the surface area you are coating, you will have the volume of zinc you are using. You can, if you wish, then multiply this by the density of zinc to convert the zinc usage to weight instead of volume.

Your unknown at this point, though, is how much surface area you are coating. Telling us the weight of steel you are coating doesn't help us because if we don't know the thickness of the steel we cannot convert its weight to its area.

As for how to reduce the thickness from 100 microns to 85 microns, we have many threads which address that issue, including:
letter 55032, "How can we minimize galvanize coating thickness",
letter 57597, "Reducing variance in galvanizing coating thickness"
and letter 45551, "Reducing coating thickness by adding nickel salts". Good luck.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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September 12, 2017

Q. How to estimate cost for chemical consumption per kg production, labour charges per kg ?

Roshan C Ugale
Sham Enterprises - Nasik, Maharashtra, India

February 12, 2019

Q. I need a GSM of a material with 500 they showed me micron level of 30 on both side totaling 60.
My question is whether we need to take one side of micron level or both sides?

siva kumar
Indway prime energy - Coimbatore, Tamilnadu, India

February 2019

A. Hi Siva. I assume you are saying that you are supposed to offer a coating of 500 grams / meter2 but don't know whether this is per side or total? Most specs mean total weight of zinc on both sides put together (although it's always dangerous to ask a 3rd party to guess what your customer wanted).

It's okay to estimate for your own purposes the grams / meter2 from the thickness, or vice versa, per the examples worked out on this page -- such that, yes, 60 microns average total thickness should be about 430 grams / meter2 -- but I think you are expected to verify the coating weight by stripping and weighing, not by taking a thickness reading at a couple of points and assuming that the thickness will be the same everywhere. Good luck.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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March 6, 2019

Q. Hi,
How much zinc coating is needed on 2.45 mm wire to get to 2.50 mm size.


March 10, 2019

A. That's an easy question. Even easier than 'What is the meaning of life?' If your wire is 2.45 mm in diameter and you want to build it up to 2.50 mm, then you need 0.025 mm of plating, since you plate all around the wire. That's 25 micrometers. And the meaning of life? That's 42. At least according to Douglas Adams.

Tom Rochester
Plating Systems & Technologies, Inc.  
Jackson, Michigan, USA
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Tom is the author of
"Surface Area Formulas & Tables
- A Resource for Surface Finishers"

sidebar2 March 2019

thumbs up sign  You'd think Adams would have learned something from Hitchhiking the whole damn Galaxy! The whole universe, no matter how vast & intricate has no significance at all without consciousness ... and whether it's even there or it isn't becomes a meaningless moot question. Consciousness is the universe's greatest achievement.

The meaning of life is to be conscious and grateful, to strive to be happy, and to help others be happy.

(That's only 21 words, not 42, so maybe it's half-baked).

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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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June 11, 2019

Q. Sir can we use Elkometer for measurement of galvanize coating.

Sharad Srivastava
- rawatbhata rajasthan india

June 20, 2019

A. Elcometer is a brand name of an instrument maker. They make many different instruments.
Your question isn't specific enough.
Which meter do you wish to use?
What do you want to measure?

If you wish to measure the length of the coated item, then a tape measure might do.
If (as I suspect, but you didn't say), you wish to measure the galvanizing thickness, then an instrument is available for this purpose, and ISO 1461 [affil. link to spec at Techstreet], the International standard for galvanizing allows for such an instrument to be used. There are many manufacturers of such instruments, Elcometer is one of many reputable brands.
The standard dictates how many places you should measure, and how to decide where etc.

Geoff Crowley
Geoff Crowley
Highland Galvanizers - Glasgow, Scotland

August 27, 2019

Q. An iron rod with 16 mm thickness without any galvanization, then what's the thickness of iron rod after the galvanization?

Rahul Parsodkar
- Wardha, Maharashtra, India

A. Sorry Rahul, that one is unanswerable.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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October 13, 2019

Q. What is the thickness zinc for 25 mm dia and get 350gsm coating

- Pune Maharashtra India

October 2019

A. Hi Nilesh. Several people have said 610GSM is 85 microns, and 430GSM is 60 microns, so 350GSM would be 350/610 x 85 = 48 microns; or 350/430 x 60 = 48 microns average thickness. But again, the math does not guarantee even thickness.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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November 21, 2019

Q. Hi there,
May I know how many micron is ZF100 Galvanneal coating and the hardness?
Thank you.

steel door manufacturer - Kuala Lumpur, Malaysia

December 2019

A. Hi Mun. ZF100 means the coating weight is 100 grams per square meter (and that usually includes both sides). I think you need to consult a manufacturer's data sheet for the hardness.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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February 5, 2020

Q. My question is I want to build up 150 microns of zinc coating by hot spraying using zinc wire.
How I will get the exact weight of the zinc to be used.

Bappu kaithakath
- Gujarat, india

February 2020

A. Hi Bappu.
Weight = Density X Volume, and
Volume = Surface Area X Thickness

You're making me guess :-)
Do you know the exact surface area you are trying to cover?
Did you know the math, but are actually asking for the density of sprayed zinc to plug into the formula?


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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February 18, 2020

Q. Greetings to all, My name is Rukesh.

I am from Malaysia. I am working in a galvanizing plant which has a production tonnage of almost 1800000 kg to 2000000 kg per month. I have a query regarding the cost comparison between using surface area calculations and also using weight difference.
My steel item has a surface area of: 2.485 m2 (FENCING ITEM)
The thickness of the steel is 5 MM.
The micron we recorded after dipping was 150 Micron which translates to about (150 x 7.2=1080 grams/m2)

Using Weightbridge
The weight of the item before galvanize: 11.5 kg for one piece.
The weight of the item after galvanize: 12.5 kg
Zinc pick-up: 8.7% and almost 1 kg

Using Surface area calculations
Surface area calculations shows pick up of:-
Total grams/m2 zinc deposited: 1080 x 2.485=2683.8 grams deposited on 2.485 m2 of surface area. In Kg, 2.684 kg.

We could observe that for that one piece of weight of zinc pick-up shows:-

For using weighbridge: 1 kg zinc pick up
For using surface area calculations and micron: 2.683 kg.

May I ask why is there a difference in weight by almost 1 kg and also is it more accurate to use the surface area calculations compared to weight difference of incoming and outgoing?

The comparison is made with the same item and of one piece sample size.

Would really appreciate if I could get a feedback regarding this matter as the difference in weight is quite significant.

Best regards,

Rukesh Prushothman
Malaysian Mega Galvanizer SDN. BHD - Petaling Jaya

February 20, 2020

Q. Sir can you tell me the formula for converting microns to gsm in metals?

Katakam saathwik
- Warangal, telengana,india

February 2020

A. Hi Katakam. As you can see from the above question from Rukesh, it can be a bit difficult in practice, but in theory it's very easy ...

Weight = Volume X Density, and
Volume = Surface Area X Thickness, so
Weight = Surface Area X Thickness X Density.

Because there are 10,000 cm2 per m2 of Surface Area, and 1/10,000 of a cm in a micron, the numbers work out nicely, with 1 micron thickness over a square meter being equal to 1 cm3 of metal. So the gsm per micron thickness is, happily, simply the density of the metal per cm3.


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

March 15, 2020

Ed. note:
abstract questions

Q. Sir, I have sample wire of 1.6 mm dia. Before zinc coating its weight is 3.19 gm, and after 3.27 gm. So I want to calculate zinc coating weight in gm/m2. Please explain with proper formula and brief calculation.

Mahendra Choudhary
India - Jaipur, Rajasthan India

March 2020

A. Hi Mahendra. I punctuated your posting and hope I am interpreting it correctly. It seems quite unlikely that you neither know nor are able to measure the length of a wire, so I'm assuming that this is a student homework question rather than a real-world situation? Therefore I'll offer you the path to solving it rather than the answer.

If you don't know the substrate material, the problem isn't solvable. But if this is a galvanizing situation and we assume that the substrate is steel --

- Once you know the substrate material, you can estimate its density.
- And knowing the weight and density, you can solve for the volume of wire you have.
- And knowing the volume and the diameter, you can solve for the length.
- And knowing the length and diameter, you can solve for the surface area.
- And knowing the added weight of the zinc coating per square meter and the surface area of the wire, you can solve for the gm/m2. Good luck!


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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May 11, 2020

Q. My steel plate of 920 x 375 x 1.4 mm
Weight - 4000 gm
Coating - 67.5 micron
How to calculate GSM of that plate

- Ahmednagar, India

May 2020

A. Hi Swapnil. If you ask a question you don't really understand, the answer isn't of much value; are you sure you understand the question? (The reason I wonder is because you gave five pieces of info and four of them are extraneous: neither the dimensions of the plate nor its weight matter).
If a coating is 67.5 millionths of a meter thick, the volume of the coating on one side of a square meter of surface is 67.5 millionths of a cubic meter, and zinc weighs about 7140 kg per cubic meter, so the weight of the coating on that square meter is 0.482 kg or 482 grams per side. Good luck!


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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May 31, 2020

Q. We are using continue galvanizing furnace for wire rod zinc plating of dia (1mm to 5mm). I want to know how to calculate the DV of galvanizing furnace, zinc thickness for formula for different wire dia., and how to calculate speed, and dip length.

Dinesh Kumar
engineering student - Ludhiana, India

May 2020

A. Hi Dinesh. I'm not a galvanizer and can't answer your questions. Sorry! But as site curator I think you'll improve the chances of readers spending their time by realizing that people would like to learn something from you ... and they want to help an actual individual ... and they seek the satisfaction of helping to solve an actual problem ... and most of them don't relish looking stuff up in books and quoting it.

If you don't get quick responses, please humor me and try to add to your question in one or more of those ways. Thanks!

Oh! And one more thing people sometimes like to do: if they feel that someone is lecturing someone else, they like to prove them wrong. So maybe my posting will help you after all :-)


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Ted Mooney, P.E. RET - Pine Beach, New Jersey
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