How can hot-dip steel be dulled or deglared?
Some types of steel come out of the kettle with a matte gray finish and others come out of the kettle with a bright and shiny finish. The type of finish you will get depends on the chemistry of the steel. There are some chemical treatments that can dull the finish such copper sulphate solutions and zinc phosphate solutions; however, these can damage the coating and have unpredictable results. This Dr Galv article discusses these chemical solutions in more detail.
It is important to note the galvanized finish will assume a matte appearance once the zinc patina forms. This is a natural process and happens as the zinc reacts with the environment and can take six months to two years. This is the preferred method for getting a dull finish because it does not decrease the service life of the galvanized coating, like chemical solutions can.