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topic 21692


A discussion started in 2003 but continuing through 2019





A. The density of zinc is 7.4 g/cm^3; there are 10^4 µm in a cm, so there are 10^12 µm^3 in a cm^3. Therefore 1 µm/m^2 is equivalent to 7.4X10^-4 g of zinc.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


A. Trevor, the danger in this type of calculations is that one gets confused about all the different dimensions. The calculation I use is (using dimensions that are commonly used in the world of coatings): Weight of coating/mtr2 [grams/m2] = Film thickness [µ] x specific weight [grams/cm3].

In the case of Zn: sp. weight is 7,4 grams/cm3: Zn weight/sqm = 7,4 grams/µ

Calculation is applicable with any coating, p.e. powder:

How much powder is on a part of 3 m2 with an average DFT of 80 µ and a specific weight of powder of 1.3 kg/dm3? Answer: 80 x 1.3 x 3 = 312 grams.

Remmelt Bosklopper
Remmelt Bosklopper
- Enschede, The Netherlands

August 25, 2014

A. I can Simplify the calculation method for converting gr/m2 to micron or micrometer.

D(density) = Wt. (weight)/ V (volume)
for Zinc
D = 7.4 g/cm3
= 7.4/cm*cm*cm.
1 cm = 10000 micron or micrometer.
= 7.4/cm*cm*10^4 µ.
10^4 µ = 7.4 g/cm*cm.
1 m = 100 cm.
10^4 µ = 7.4 g*100*100/(100*cm)*(100*cm).
10^4 µ = 7.4 g* 10^4/m*m.
1 µ = 7.4 g/m2 for one face.
1 µ = 14.8 g/m2 for two face.

for galvanization layer
25 µ = 185 g/m2 for one face
and 25 µ = 370 g/m2 for two faces.

Nagy Emara
Kandil Steel - 10th of Ramadan - Egypt

May 2, 2019

Many of my customers are asking that you says it's 90 GSM, but can you tell in micron, and at that time I am unanswerable, so please let me know how to calculate micron to GSM and vice versa

R.Ashok Gour
- CHENNAI, tamil nadu, India

May 2019

A. Hi Ashok. They can measure the thickness of the galvanizing with a magnetic thickness meter if they wish confirmation.

Remelt has told us that 1 micron is about 7.4 GSM; so 90 GSM would apparently be somewhere around 12 microns. However, as Nagy implies, it is conventional that 90 GSM refers to the total amount of zinc applied to both sides of the strip, so I would expect the thickness to be about 6 microns per side.

You can refer them to this page where the question has been answered. Good luck.


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

May 3, 2019

A. Most sources give the density of pure zinc as 7.14 g/cc. It will be slightly higher for Prime Western Zinc which is a zinc-lead alloy (up to 1.4% lead) but not much. The vast majority of hot dip galvanizing, until recently, was done with Prime Western Zinc. Other alloying components (aluminum, nickel, etc.) will have calculable effects on the density of the coating.

Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
plating systems & technologies banner ad

May 2019

thumbs up sign  Thanks for the more refined answer, Tom. 90 GSM equals about 13 microns.


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

sidebar2 July 24, 2019

Q. If I have a paper that is 32GSM what would be the approx. micron thickness.

Anthony Cuschieri
International Packaging FIlms (PET Film)s - Norwood, New Jersey USA

August 2019

A. Hi Anthony. Although I don't know much about paper, a roll of coated magazine paper weighs far more than an equal size roll of toilet paper. So I think your question isn't answerable because the density of different papers can apparently vary by about 4:1, maybe more.


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