How To Tell If Sheet Metal Is Galvanized

How do you know if steel has been galvanized.

How to tell if sheet metal is galvanized.

During this period it is usually easy to tell if the steel has been hot dip galvanized just by looking at it. Galvanizing coats the steel with a layer of zinc the two look different. Zinc is more of a dull grey color if hot dipped if it s shiny you can usually notice kind of a crystalline look to it. Dip an old cloth into the salt and water saline solution and wipe it on the sample of steel.

Galvanized metal is a form of steel that has a thin coating of zinc oxide. Different methods are used to galvanize metal including hot dipping pre galvanizing and electrogalvanizing. The drum is then superheated to 500c. Hot dip galvanizing gives the large kinda blochy crystal structure or pattern that is most readily identified as galvanized metal.

At temperatures above 300c zinc turns into a vapor and this vapor penetrates the metal turning inside of the drum. Prepare a solution of three parts salt to one part water that will be used to test the steel sample. You can tell that metal is galvanized when it has a pattern to it that is known as a spangle pattern. Over time however natural weathering processes and brown staining may make it harder to determine if the steel was galvanized.

1 hot dip galvanizing and 2 electrogalvanizing. Zinc also acts as a sacrificial anode meaning even if the zinc coating is damaged in some way the remaining. Think of steel culverts as an example. There are 2 main methods to galvanize metal.

The metallic parts that are to be galvanized are put inside of a closed rotating drum along with zinc powder and sometimes a filler like sand. Visual clues and other testing can determine which coating system was used. A spangle pattern almost looks like someone dipped a sponge in gray paint and then sponge painted the metal. A hot dip galvanized coating may show a high zinc content near the outside of the coating with an increased iron content near the metal substrate.

A zinc metallized or mechanically plated coating will contain a high zinc content through the entirety of the coating.