In a previous post, we had discussed the topic of how zinc-coated Unistrut can provide resistance to acids, salt, and other environmental factors that would cause uncoated Unistrut to rust. Knowing that there are endless uses for our Unistrut channel and fittings, we want to dive deeper into what finishes are available and which are best for what environment and usage.
What is the common use for Plain Finish Unistrut channel?
Plain Unistrut is susceptible to rust and offers the least amount of corrosion resistance. That said, because it is plain, this channel style is ideal for projects requiring welding or powder coating. See below for a breakdown of the Plain finish.
PLAIN (PL) finish is commonly used for most indoor applications. The raw steel will retain the oiled surface. Typically, the channel let’s say P1000 will be welded or will be painted a specific color to the needs of the application. To lessen the rust, use a paint primer or powder coating. Plain is the only finish that we recommend if needing to weld.
What if I need a more protective finish than the Plain?
Unistrut Perma-Green III goes above and beyond when it comes to commonplace finishes — mainly used for Unistrut Channel, as in the P1000T, there are also a select few brackets and fittings that bear the Perma-Green III finish. Perma-Green III uses an environmentally neutral process that virtually eliminates toxic metals found in other paint-based finishes. Compared to other “high-performance” coatings, Perma-Green III is proven to have resistance to fading, chalking, and checking and is far less vulnerable to solvents and typical acidic atmospheres. Being extremely durable, Perma-Green III can be used for indoor and outdoor applications.
What other corrosive-resistant options are available?
Rust can play a big part within a Unistrut application. Selecting the channel or fittings that are zinc coated is an easy way to minimize corrosion associated with outdoor applications as well as corrosive inside environments.
ZINC COATING
Unistrut produces the following zinc coatings:
- Electroplated (EG)
- Pre-galvanized (PG)
- Hot Dipped Galvanized (HG)
There are two main types of protection that zinc offers
- Barrier: The zinc coating protects the steel from direct contact with the environment it is in.
- Sacrificial: The zinc coating protects from scratches or cut edges to ensure limited corrosion.
Remember, the service life of the zinc coating is directly related to the coating thickness, as shown below.
ELECTROPLATED ZINC (EG), the most common of finishes when it comes to Unistrut fittings. P2950 and P2949 are just two of the many Unistrut fittings/trolleys that come in this finish.
PRE-GALVANIZED ZINC (PG) is the most common finish for channel. The steel strip is uncoiled, fed through a continuous molten zinc coater, and then recoiled, producing clean, fluxed, Zinc steel. This finish is a time-tested, well-proven coating for outdoor and indoor applications. If needing a more severe corrosive finish Hot Dipped Galvanized will be a great alternative. As shown in the graph, when the zinc coating is doubled, the service life is doubled under most conditions.
HOT DIPPED GALVANIZED (HG) is used for both Unistrut channel and fittings, this is the chosen finish for where applications will be in a severe corrosion setting. The finished part is fully immersed within a bath of molten zinc, giving the Unistrut part a full coverage of zinc and a thicker coating than pre-galvanized and plated zinc. Street guardrails and highway signs typically are hot-dipped galvanized, and that shows how durable the finish can be.
Meet Unistrut Defender – The Cost-Effective Alternative to Stainless Steel
UNISTUT DEFENDER (DF) is designed for harsh environments and is 3 times more corrosion resistant than hot dipped galvanized from independent studies. Unistrut Defender is a combo of two propitiatory material coatings conforming to ATSM standards A1046 and A1059. DF is much more corrosion-resistant than HDG but significantly less expensive than stainless. Please note that Defender is not available in all channel and fitting styles, contact Unistrut Service Company for more information on Defender.
Parting Thoughts
Sometimes folks think that finish is the only variable to consider when corrosion resistance is an issue. As you can see below, by selecting the right material, you’ll achieve varying levels of corrosion resistance for a given application.
Refer to the chart below to quickly review finish choices and make the proper specification for your application.
Need Additional Assistance?
Our goal is to provide you with the information and expert guidance needed so you can select the right Unistrut material for your specific application. Be sure to read our blog regularly and consult our literature library for the latest information on this versatile building material. While we do our best to provide all the technical information you may need, we understand that your application can be unique. You may have additional questions that can’t be answered by reviewing our website. To discuss your application in greater detail, request pricing, or to place an order, contact Unistrut Service Company by phone at 1-855-923-2611 or send us an email using our Contact Us Form.