Monday, May 20, 2013

Duplex System Compatibility


What Paints and Powders are compatible with Galvanizing?

A partial listing of available paint, paint systems,
and powder coatings that are compatible with
galvanizing are listed in the following table. The
paint manufacturer can provide more thorough
information about the compatibility of specific
systems with galvanized steel. Always consult
the paint manufacturer prior to painting galvanized
steel. Different physical and chemical characteristics
for the same types of paint may have varied reactions
with a galvanized surface. The paint manufacturer and
galvanizer can assist in the creation of a successful
duplex system.

Type
Compatibility
Comments
Acrylics
Sometimes
If the pH of the paint is high, 
problems may occur due to
ammonia reacting with zinc
Aliphatic Polyurethanes
Yes
If used as a top coat for a 
polyamide epoxy primer, it
is considered a superior
duplex system
Alkyds
No
The alkaline zinc surface causes
the alkyds to saponify, causing 
premature peeling
Asphalts
No
Petroleum base is usually not
recommended for use on
galvanized steel
Bituminous
Yes
Used for parts that are to be
buried in soil
Chlorinated Rubbers
Yes
High VOC content has severely
limited their availability
Coal Tar Epoxies
Sometimes
Rarely used, only if parts are to
be buried in soil
Epoxies
Sometimes
If paint is specifically
manufactured for use with
galvanized steel
Epoxy-Polyamide Cured
Yes
Has superior adherence to
galvanized steel
Latex-Acrylics
Yes
Has the added benefit of being
environmentally friendly
Latex-Water-based
Sometimes
Consult paint manufacturer
Oil Base
Sometimes
Consult paint manufacturer
Portland Cement in Oil
Yes
Has superior adherence to
galvanized steel
Silicones
No
Not for use directly over 
galvanized steel, can be
beneficial in high temperature
systems w/ base coat
Vinyls
Yes
Usually requires profiling, high
VOC’s have severely limited
their availability
Powder Coating
Yes
Low temperature curing powder
coatings work exceptionally 
well over galvanized steel