Steel Manufacturing Blog: Keeping it Steel

Galvanized Vent Hole Plug Series: Aluminum vs. Zinc

Posted on Thu, Jan 07, 2021 @ 03:38 PM

All vent hole plugs are designed for the same purpose, to seal the vent and drainage holes made in a steel component during the galvanization process. While their functionality is simple, the choice of whether to use aluminum or zinc vent hole plugs can be more complicated.

Aluminum is the economical option, but it is a different metal than the zinc used to coat steel during galvanization. All metals have a different electrical potential, as shown by the diagram below.


When two different metals with different electrical potentials are in contact and share a conductive medium, a “galvanic cell” is formed. A galvanic cell is similar to a battery. The metal with lower electrical potential becomes an anode and the metal with higher electrical potential becomes the cathode. The conductive medium (i.e. water) allows for electricity to pass between the two metals. The metal with a lower electrical potential, the anode, will undergo accelerated “galvanic corrosion”.


Imagine a piece of zinc coated steel that uses an aluminum vent hole plug in a place that is exposed to water in the form of humidity or rain. The water acts as the conductive medium between the two metals, and causes a galvanic cell to form.

In these situations, it may be pragmatic to use a zinc vent hole plug, as it is the same metal as the zinc coating created during galvanization. By using the same metal, no electrical charge can be passed between the two materials, and no galvanic corrosion can occur.

In general, however, aluminum vent hole plugs are sufficient. The difference in electrical potential between aluminum and zinc is fairly low so the rate of galvanic corrosion will not be so high that corrosion would effect the performance of the plug or zinc coating. Additionally, the surface area of both materials should be considered. A vent hole plug accounts for only a fraction of the surface area of the steel component it is being used on, which greatly inhibits the ability for galvanic corrosion to occur and the overall effects will be minimal.

As always, our sales representative are ready and waiting to assist you with any questions you may have regarding vent hole plugs or any other products we sell! You can submit any questions you might have on our form below, or via the info/request forms.

Tags: Vent Hole Plugs