Fasteners In Salt Water Environments: What You Need To Know

Fasteners In Salt Water Environments

One of the biggest complaints we hear about are fasteners rusting prematurely. The first question we are likely to ask is “Are you within 20 miles of a salt water environment?”

Surprisingly, an overwhelming amount of customers say yes. It is commonly understood that metal rusts and that it rusts worse in corrosive environments. It is not commonly understood that those environments spread beyond what the eye can see, however, this should be one of the bigger factors taken into consideration when buying fasteners.

Stainless steel is a prime example of this. Almost anyone you talk to can tell you stainless steel is corrosion resistant, but did you know that grade 410 stainless steel is less corrosion resistant because it is heat-treated to be harder? or that grade 304 stainless is not suited for highly corrosive environments?

In fasteners, the material and sometimes even the grade matter when it comes to choosing the right fastener for your installations. There are several materials that do extremely well in salt-water environments, some that kind of work and some that are almost guaranteed to fail.

What You Should Use

There are generally a few materials that work extremely well in salt-water environments. Depending on your needs you should aim to choose from the following:

Grade 316 Stainless Steel
Aluminum
Silicon Bronze

These materials (or specific grades) are ideal for salt-water environments because they can resist the corrosive effects that salt-water very well.

Another option to try is HDG (Hot Dip Galvanized) fasteners. HDG is a form of zinc coating that will protect the fastener from harm and is usually a cheaper option but is not a perfect solution.

HDG fasteners can handle well in certain salt-water environments but results can vary depending on if they are submerged, water temperature and air temperature. Due to these factors, we do not recommend it as it will likely not perform as well as the materials listed above.

Pro Tip

Although 316 stainless steel and aluminum are both listed as good materials to use in corrosion resistant environments, you also do not want to mix the two. If you do, the process of galvanic corrosion is more than likely to occur, resulting in a significantly shortened lifespan for your fasteners.

To see the fasteners we carry in these selections check out our marine grade and aluminum fasteners pages.

What Screws Should You Use For Building A Deck?

Building A Deck This Summer?

Having a deck in your home is a luxury many people enjoy having. Being able to sit outside and enjoy the weather or view with family and friends is an excellent way to spend nice days, especially with summer right around the corner.

If you decide to take the journey of building a deck yourself, you are going to have many questions along the way. One of the most important points to consider is “Which screws should I use for this deck?”. We’ve heard this question before and there are quite a few things to take into consideration.

1. What Material Should I Use?

Of all the available materials to use for your deck, the most common is stainless steel. Stainless steel deck screws offer an excellent solution due to their increased corrosion resistance. However, stainless steel can still corrode in certain situations so make sure you have the correct grade for your environment.

2. Do You Want To See The Screw Heads?

One of the biggest concerns when making your deck is choosing the correct screw head. Deck screws are usually only found in flat head varieties so they can sit flush with the wood once installed. The question remains, do you want to see the head?

If your answer is yes, then a standard stainless steel flat head deck screw will suffice. If your answer is no, then you have a few options for hiding the screw heads.

Painted Head Deck Screws – These stainless steel screws are stainless steel with painted heads to match common wood colors. They are the easiest way to hide a deck screw because they are camouflaged in plain sight. Just install them as you would any other deck screw.
Hardwood Plug Kits – These kits come with little wood corks that you can use to cover the screws. They require more work to install properly but usually leave a great result. First a countersunk hole must be made to sink the screws lower into the wood. Then an adhesive is applied to the plug and placed in the hole over the screw head. One downfall to this method is that removing them is difficult. You can also get a drill bit that can cut these plugs for you instead of buying a kit: Hardwood Plug Cutter Bit.
Ipe Clips – A third and quickly becoming a very popular option are Ipe Clips. Ipe Clips are installed between the boards of a deck hiding the screws entirely. Mostly used with Ipe wood, these clips can also be used with regular wood to help create an evenly spaced deck.

What Drive Style Should I Use?

Usually, there are three types of drive to consider here. Phillips, Square or Star drive. Although all three are decent choices, we recommend using the star drive for installations. The star drive has the least chance of slippage and cam out during installation making it the ideal choice when working with finished products where slipping out of the drive could damage the surface you are working on. In fact, on many decks built today you are more likely to see star drive screws being used.

Building a deck can be a daunting task but with the proper screws you are now one step closer to enjoying your yard and the weather this year.

Stainless Steel Applications

Stainless steel is used primarily for long-lasting applications, due to its corrosion-resistant nature and durability. At Albany County Fasteners we stock fasteners various stainless steel grades to provide an appropriate solution for any fastener application.

Stainless Steel Grades:

18-8 Stainless Steel – (18% Chrome, 8% Nickel, .08% Maximum Carbon) – This is the standard grade for stainless steel fasteners. They are corrosion-resistant and durable. They are often used in marine applications in freshwater environments, but will not work as effectively in a salt water environment.

304 Stainless Steel – (17%-19% Chrome, 8%-12% Nickel, .08% Maximum Carbon) – This is a superior grade of 18-8 stainless steel. 304 Stainless steel is often used to make Machine Screws, Cap Screws, Sheet Metal Screws, Hex Cap Screws and all cold headed or hot forged fasteners. It is often used in food service and dye applications because of its ability to resist the corrosive properties of organic acids.

305 Stainless Steel – (17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon) – This grade has been developed specifically to improve the cold heading qualities of 18-8. This grade does not work-hardened products are actually made from this grade even though they are referred to as being made from type 304 Corrosion resistance and physical qualities are equal to Type 304. 305 stainless steel is used to make deck screws, which are used (shockingly) to fasten wood or composite boards to the main beams of a deck.

Square Drive Deck Screw-305 Stainless Steel

316 Stainless Steel – (16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum) – This grade of stainless steel is used and recommended for applications in severe or harsh environments. Its corrosion resistance is greater than 18-8 stainless, which is why we recommend using 316 stainless steel fasteners for salt water environments. It is important to remember that even the salt in the air near a body of salt water can do damage to dry applications, so 316 is the material of choice. Common applications of 316 stainless steel fasteners include boats, docks and piers.

410 Stainless Steel – (11.5%-13.5% Chrome, .15% Maximum Carbon) – Due to the fact that this grade of stainless steel can be hardened up to approximately 40 Rockwell C, it is durable in most environments. It is commonly used to make roofing screws and siding screws and self tapping (or self drilling) screws, because it is a harder material than the metal being fastened in these types of applications.

What Do the Numbers Mean?

Stainless Steel Grades

Stainless steel fasteners are defined by the grade of the material. Now what exactly does this mean? See the list below for information on common grades of stainless steel fasteners including material and common applications.

- Type 304: 17%-19% Chrome, 8%-12% Nickel, .08% Maximum Carbon. This is a superior grade of 18-8 stainless steel and is used for Machine Screws, Cap Screws, Sheet Metal Screws, Hex Cap Screws and all cold headed or hot forged fasteners. It is an equivalent to 18-8 Stainless Steel.

- Type 305: 17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon. This grade has been developed specifically to improve the cold heading qualities of 18-8. This grade does not work-hardened products are actually made from this grade even though they are referred to as being made from type 304 Corrosion resistance and physical qualities are equal to Type 304.

- Type 316: 16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum. This grade is greater corrosion resistance when used with certain acids as compared to general range of 18-8 stainless steel. 316 Stainless Steel is used in saltwater application such as boats and docks.

- Type 18-8: 18% Chrome, 8% Nickel, .08% Maximum Carbon. Used in most fasteners and is the standard.It is an equivalent to 304 Stainless Steel.

Type 410: 11.5%-13.5% Chrome, .15% Maximum Carbon. This grade can be bright and hardened up to approximately 40 Rockwell C. This is used in roofing screws and finishing washers.

What is Thread Galling?

How To Combat Thread Galling

Stainless Steel Fasteners locking up? It’s probably thread galling, not the quality of the parts but the common problem of using stainless steel fasteners.

The beneficial nature of using stainless steel is that it is corrosion resistant. This property is due to the fact that stainless steel, among other alloys, generate a protective oxide surface film. Though this is beneficial as it provides corrosion and rust resistance, it can sometimes lead to problems with installation.

Thread Galling occurs during fastener tightening and installation. When pressure builds between the contacting surfaces of the male and female threads, the protective oxides or coatings begin to shear, causing high points, or imperfections in the raw material to become locked together. The increase in friction causes the two parts to seize or “lock-up”. In serious cases, this problem is even referred to as “cold welding”, which illustrates the severity of the issue. Often, galling can cause damage to the thread of the fastener, but it can still be removed. In severe cases, the two materials completely weld together preventing loosening of the parts, and adding the difficult step of a forced removal and new parts to the process. The frustrating aspect of this is that both the nut and bolt can clear inspection individually, but fail to function effectively as a mechanical unit.

Though this problem may be frustrating, it is avoidable. The main issue to address is to decrease the friction between the adjoining parts. This can be done in several ways including a slower installation process (RPMs). The idea behind this method is to reduce the friction (and thus heat), between the parts preventing the “welding” process. Our recommended method, due to its ease of implementation, is lubrication. Common methods include specially designed lubricants and waxes, however due to its safety and ease of availability, we recommend dipping the bolt in Maalox.

Update: Maalox is no longer sold at stores so we started carrying an anti-seize solution that we’ve tested ourselves.

Introducing MRO ANTI SEIZE SOLUTIONS!

MRO Anti Seize solutions are tested lubricants with carefully manufactured specifications. Each type has unique characteristics which can be found on the individual product pages. We carry several different kinds of anti-seize to make sure we can offer a solution that works for you!

Anti-seize solutions offer many benefits to fastener installations. Not only do they provide fasteners with a layer of lubrication that reduces friction, the coating also creates an extra layer of lubrication and corrosion resistance to make your fastener assembly last even longer!

Other precautionary measures include using coarse threaded fasteners, using different grades of stainless steel for adjoining parts (take the corrosion resistance differences into consideration), and understanding the proper use of lock nuts. Because they are designed to add resistance to the existing threads of the bolt, it is best practice to make sure that a minimal amount of threads extend beyond the nut.

Reducing friction is the preemptive strike against this problem. That is why we recommend lubrication, and MRO anti-seize specifically, due to many of its properties beneficial to both sore stomachs and stainless steel. Galling can be a frustrating problem, but it can be prevented.

If you need any more information on thread galling check out our Fasteners 101: Thread Galling Resource page for more information.

In This Video:

Our Fastener Expert explains galling, shows us an example and then explains how to prevent it with an MRO Anti-seize Solution.

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Category: 316 Stainless Steel