How To Tell If Sheet Metal Is Galvanized

Steel is usually primed if not surface rust will be noticeable.

How to tell if sheet metal is galvanized.

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. Dip an old cloth into the salt and water saline solution and wipe it on the sample of steel. How do you know if steel has been galvanized.

Hot dip galvanizing gives the large kinda blochy crystal structure or pattern that is most readily identified as galvanized metal. A spangle pattern almost looks like someone dipped a sponge in gray paint and then sponge painted the metal. Visual clues and other testing can determine which coating system was used. 1 hot dip galvanizing and 2 electrogalvanizing.

At temperatures above 300c zinc turns into a vapor and this vapor penetrates the metal turning inside of the drum. How to test to see whether steel is galvanized step 1. Different methods are used to galvanize metal including hot dipping pre galvanizing and electrogalvanizing. Galvanized metal is a form of steel that has a thin coating of zinc oxide.

You can tell that metal is galvanized when it has a pattern to it that is known as a spangle pattern. Prepare a solution of three parts salt to one part water that will be used to test the steel sample. 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. During this period it is usually easy to tell if the steel has been hot dip galvanized just by looking at it.

Zinc also acts as a sacrificial anode meaning even if the zinc coating is damaged in some way the remaining. The drum is then superheated to 500c. Over time however natural weathering processes and brown staining may make it harder to determine if the steel was galvanized. Think of steel culverts as an example.

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.