Corrosion in Coastal Environments

An ounce of prevention is worth a pound of cure

– Benjamin Franklin

Any contractor that has ever had to replace a corroded connector or fastener will tell you this quote is an understatement. Here at Simpson Strong-Tie, we spend a lot of time refining new product designs to simplify their installation, but uninstalling a joist hanger? It never crosses our minds, and it shows by looking at all the tools you would need: claw hammer, cat’s paw, reciprocating saw, and the all-important first aid kit.

But luckily for the project owner, an ounce of prevention only costs about the price of half a pound of cure. Stainless steel connectors and fasteners are in the range of 5-10 times the cost of galvanized steel. However,  connections are usually only a small part of a project’s overall budget and are a critical part of the load path, so the argument for stainless steel is an easy one to make.

The term stainless steel (SS) applies to any steel alloy containing at least 10.5% chromium by mass. There are dozens of SS alloys available, each with different properties and levels of corrosion resistance. Without turning this into a metallurgical blog post (which I can barely spell, let alone write about), let me just say that many grades of SS are not suitable for coastal or other corrosive environments.

The most common SS alloys used in the construction industry are Type 304 (aka “18-8”), Type 316, and Type 410. Type 316 provides a higher level of corrosion resistance than Type 304, especially in coastal and other high-chloride environments (all of our SS connectors are Type 316L – the L is for low carbon).

Specialty stainless steel fasteners can be a little more complicated than connectors due to manufacturing. Softer steel may be needed for head forming, whereas higher hardness may be required to for breaking torque of a screw. So specialty fasteners may be manufactured with different types of stainless steel. Simpson Strong-Tie uses all three common SS alloys in our fasteners, but we recommend using Type 410 in low corrosive environments only. The Specialty Steel Industry of North America publishes an informative design guide, including a downloadable portion on the selection and use of stainless steel that has detailed information on the many SS alloys.

The concentration of salt spray in the air decreases drastically between 300 and 3,000 feet from the shoreline, but keep in mind that corrosion is not just a coastal issue. Exposure to chlorides from road salts and melting salts placed on walkways poses a significant corrosion threat to exposed steel in colder climates. So when designing in a corrosive environment, I will offer another of my favorite quotes: steel (even stainless steel) is cheaper than lawyers.

Here are some other useful industry resources available for download:

– Paul 

One thought on “Corrosion in Coastal Environments

  1. Paul,
      Thanks for the information it was interesting. I used to live in and was a contractor in Hawaii and you’re right stainless steel is the way to go. Thank you also for the links. I still have many builder friends in Hawaii that i’ll send these links to.

Leave a Reply

Your email address will not be published. Required fields are marked *