The hot-dip galvanized coating is an intermetallic layer of iron and zinc, meaning the zinc and iron react and diffuse into one another to create the galvanized coating. If more iron is available to react with the zinc, a thicker coating can develop. Thicker pieces of steel tend to develop thicker galvanized coatings. Steel chemistry also plays a huge role in zinc coating thickness, with silicon and phosphorus being the primary catalysts of the galvanizing reaction. Steel chemistry and thickness have the biggest effect on the galvanized coating thickness.

Are you still looking for the right answer? Ask an Expert


Laura Hanson

Hi Anil,

White rust is a common name for what we call wet storage stain. It appears on items that have not been properly stored. More information on this occurrence can be found on our website ( or in our Wet Storage Stain publication:

anil pandey

we r facing one problem from long time
we r pipe galvanizer
As per process we r doing every thing as pickling—fluxing—drying—galvanizing (dry process )—steam blowing—cooling—passivization with 65 degree temperature -spreed on long bed for drying each and every pipe -then pack for dispatched
these pipe when i export to u s they found on some pipe white rust and some are good,if i store in plant we have no any problem
one or two year,
i don’t understand ,what i do please suggest
am humbly thankfull to u

anil pandey

Alana Hochstein

Hi David,

There are many factors which can affect coating thickness including:  steel chemistry (silicon and phosphorus contents), steel thickness, steel surface condition, bath temperature, immersion time in the zinc bath, and withdrawal rate from the zinc bath.

There is a relationship between galvanizing time and coating weight which is available on the following page of our website:

Additionally, it is possible to see the flux boiling off (bubbles) as a visual indicator that the steel is ready for removal from the zinc bath.

david neil serate

From the above article, it is mentioned that coating thickness depends on steel thickness and from other resources saying that increasing immersion time will not increase the coating thickness. i am now confused.

Further, how will we know that the steel has heat enough and when is the right time to pull out the article from the zinc bath.

Hi Ajeet,
The effects of steel chemistry and steel thickness on the galvanized coating thickness are independent of surface area.  For thicker steel, a longer immersion time in the zinc bath is typically required to heat the steel and form the galvanized coating.  Because a longer immersion time in the zinc bath results in thicker coatings, an increase in steel thickness will tend to increase the coating thickness.

ajeet gupta

Dear Sir,
how can it be possible if the surface area for coating for thiner or thicker material will be same.

Add Your Comment