TrailerTech: Stainless Steel Fasteners in Steel and Aluminum

Welcome to the first installment of TrailerTech!

We’re launching this new addition to the blog lineup to share some technical details, facts and tips that can help you with your trailer performance endeavors. Today, we’re covering a common misconception that we’ve seen crop up over the Internet. According to some, stainless steel bolts aren’t necessarily a good idea to use in carbon steel or aluminum beams due to the process of galvanic corrosion. Our team has observed a few things during some in-house testing and we’d like to take a minute and help clear up some misconceptions.

Galvanic (or bimetallic) corrosion occurs when two different kinds of metal come into contact and are exposed to an electrolyte (rainwater, groundwater, mud, saltwater etc.) which causes an electrochemical reaction. When this electrical process occurs, one metal acts as an anode and the other as a cathode. As a result of the galvanic connection, the anodic metal decays at a much faster rate than it normally would and the cathodic metal decays much slower. Eventually, this connection causes the anodic metal to dissolve and deposit its remains upon the cathodic metal, causing rust to form.

So how big a deal is galvanic corrosion when using stainless steel hardware to fasten stuff to your trailer's frame?

To test this in-shop, we chose 300 series stainless steel due to it's high availability and common use as a fastener. We observed that although the galvanic connection is still made with electrolyte exposure, the shear size of the anode (the ample frame) greatly decreases the rate of decay. In fact, no galvanic corrosion was detected. Overall, we have found the effects of galvanic corrosion of 300 series stainless steel in carbon steel or aluminium to be greatly overstated, and consider the practice to be safe. The key understanding being that no rust is formed due to the small relative size of the stainless steel fastener within the larger piece of carbon steel. For extreme duty applications, such as continual salt bombardment during the winter time, prolonged use in saltwater or prolonged exposure to mud, a zinc chromate primer can be applied prior to assembly with stainless steel fasteners.The frame should be coated first, let dry, then the fastener coated and inserted wet. It would seem that the benefits of rust-resistant stainless steel hardware for trailers greatly outweighs the infinitesimally small risk of galvanic type corrosion.  

We hope this has provided you with some insight into using stainless steel fasteners in carbon steel or aluminium. We have more informative topics lined up, so keep an eye on the blog.