Minimum Coating Thickness

Yes it is. Hanging anything over 3mil will always cause you a problem. So the 2.5 is a gerneral because hitting 2.5 exactly is very hard so your going to run up near 3mil in some areas.

It works a lot of us estiblished this 2.5 avarage over many years of work with all kind of materails.

On battleship, air craft carriers and submarines these were coated with one water based zinc .05mil, then an alochol based zinc .05 mil, then epoxy primer 2 coats x 2.5 mil then 2 coats of epoxy fininsh coats x 2.5 mil. Then below the water line 2.5 mil of antifoulin. That was the exterior. Interior to the bilges only 1 primer and 1 finish coat.

There are no hard and fast rules of thumb - it will depend on what you're coating (steel, concrete, plastic?...), why (corrosion protection, purity, aesthetics...), what you can afford to spend, how long you want it to last, what chemicals and at what temperatures, is mechanical damage and wear a concern, ...

Coatings and linings from just a few thousandths (of an inch) up to 1/4" or more (typically glass reinforced) are successfully used in industrial applications.

Either this 'spec' is extracted (very poorly) out-of-context, or, it is poorly written to begin with.

"Dad" (post 1) needs to re-read his archived specs... there is no way (short of direct intervention by the Lord) that he or anyone else ever applied ".05 mils" of any type of zinc based primer...

A mil is not a millimeter. 1 mil = 0.001 inch, and most industrial coatings for corrosion prevention of steel do, in fact, get applied in 'many-mil' thicknesses. "Many", but NOT all.

As post 2 suggests, Coating Specifications are fairly complex documents, taking many factors (surface type, profile prepared, cleanliness, purpose, environmental exposure, etc) into account.

The OP (original post) offers less than a "fog" of understanding of the scenario, in order to provide conclusive/viable responses.

"More, please..."

No I will not take this as rule of thumb. For salt water protection of ship we need thicker coating and on other hand for scratch protection of glass we do coating in micron.

The end use if you define first then only you can determine coating thickness needs. In general if coating material is scarifying type to protect inner material then generally thicker is better.

If outer is for protection and not for scarifying thinner is better.

2.5 mm as a geenral rule seems too much.. i mean as others said it depends on what you are coating and why.. usually i've seen requirement for 400-500 micron up to 1 mm on equipment in chemical plant made in steel or alloy.. what kind of chemical is processed?

S

corrosion prevention