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.

Prepare a solution of three parts salt to one part water that will be used to test the steel sample. Dip an old cloth into the salt and water saline solution and wipe it on the sample of steel. 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. Over time however natural weathering processes and brown staining may make it harder to determine if the steel was galvanized.

There are 2 main methods to galvanize metal. You can tell that metal is galvanized when it has a pattern to it that is known as a spangle pattern. Visual clues and other testing can determine which coating system was used. Acting as a barrier between steel and the atmosphere zinc protects corrosive substances from reacting with metal which can cause it to weaken over time.

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. Think of steel culverts as an example. Galvanized metal is a form of steel that has a thin coating of zinc oxide. Galvanizing coats the steel with a layer of zinc the two look different.

At temperatures above 300c zinc turns into a vapor and this vapor penetrates the metal turning inside of the drum. A zinc metallized or mechanically plated coating will contain a high zinc content through the entirety of the coating. How to test to see whether steel is galvanized step 1. 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 spangle pattern almost looks like someone dipped a sponge in gray paint and then sponge painted the metal. During this period it is usually easy to tell if the steel has been hot dip galvanized just by looking at it. How do you know if steel has been galvanized. Different methods are used to galvanize metal including hot dipping pre galvanizing and electrogalvanizing.

Zinc also acts as a sacrificial anode meaning even if the zinc coating is damaged in some way the remaining.