How To Tell If Sheet Metal Is Galvanized

Over time however natural weathering processes and brown staining may make it harder to determine if the steel was 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. Different methods are used to galvanize metal including hot dipping pre galvanizing and electrogalvanizing. How do you know if steel has been galvanized. 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.

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. 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. Dip an old cloth into the salt and water saline solution and wipe it on the sample of steel.

Steel is usually primed if not surface rust will be noticeable. Hot dip galvanizing gives the large kinda blochy crystal structure or pattern that is most readily identified as galvanized metal. Galvanizing coats the steel with a layer of zinc the two look different. How to test to see whether steel is galvanized step 1.

A spangle pattern almost looks like someone dipped a sponge in gray paint and then sponge painted the metal. At temperatures above 300c zinc turns into a vapor and this vapor penetrates the metal turning inside of the drum. There are 2 main methods to galvanize metal. A zinc metallized or mechanically plated coating will contain a high zinc content through the entirety of the coating.

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. Think of steel culverts as an example. Visual clues and other testing can determine which coating system was used. The drum is then superheated to 500c.

Prepare a solution of three parts salt to one part water that will be used to test the steel sample.