There are various considerations to take into account before using concrete fasteners in outdoor applications. Most concrete fasteners are made from steel and may rust when exposed to moisture, salt or chemicals. Some concrete fasteners are plated, coated or made from stainless steel or are manufactured using steel that is rust resistant. Each of these concrete anchors can be ranked in their ability to prevent rusting. It is important to remember that dissimiliar materials and chemicals (such as chlorine) may also have an effect on the ability of materials to inhibit the rusting process. Stainless steel anchors come in three different grades- 303, 304 and 316. The 303 and 304 grade of stainless steel provide excellent resistance to rusting, while the 316 grade stainless steel offers superior rust resistance.
Not sure if the concrete anchor you want to use is suitable for use outdoors? Read on to find out before starting your project.
Wedge Anchors
Zinc plated wedge anchors are not suitable for use in outdoor structural applications. While they can be used for other applications, one should be aware that a zinc plated wedge anchor has a very low resistance to rust. The hot dipped galvanized wedge anchor provides moderate resistance to rust. However, stainless steel wedge anchors are well suited for use outdoors. Stainless steel wedge anchors are available in 303, 304 and 316 stainless steel. The cost of the anchor increases in proportion to the level of rust resistance the steel or coating provides.
Get more information about Thunderstud wedge anchors.
Sleeve Anchors
Sleeve anchors plated with zinc should not be used in applications outdoors. They can be used for other non-critical applications but this anchor has a low resistance to rust. However, sleeve anchors are available in stainless steel and therefore can be used in outdoor applications. Sleeve anchors are available in the 304 series of stainless steel only. The sleeve anchor comes in different head styles including the acorn head, hex head, flat head and round head.
Read more detailed information about sleeve anchors.
Tapcon® Concrete Screws
Concrete screws have a coating called Climaseal® which provides extra corrosion resistance. These Tapcons are acceptable for use in ACQ pressure treated lumber in outdoor applications. Tapcon® screws that are well suited for outdoor use include the 410 stainless steel screw which is also Climaseal® coated.
Are Tapcons the right concrete anchor for your application, order concrete screws now!
Strike Anchors
Strike anchors are only available in yellow zinc plating and are not suitable for use in structural applications outdoors. However, they can be used outdoors in non-critical applications with the awareness that they provide low rust resistance.
Get more information about concrete strike anchors.
Drop In Anchors
Zinc plated drop in anchors should not be used in outdoor structural applications. These anchors could be used in situations where the application is not critical but one must be aware that these anchors have low rust resistance. Stainless steel drop in anchors are suitable for use in outdoor applications. They are manufactured in both 304 and 316 stainless steel. The 304 stainless steel anchors are excellent for use in moist atmospheres while the 316 stainless steel is excellent for use in applications where submersion into salt water or the presence of other chemicals are an issue.
Are drop in anchors the type of fastener you need- order a drop in anchor now!
Metal Hit Anchor
Metal hit anchors are manufactured from a soft zinc metal called Zamac, which is rust resistant. This anchor has a zinc plated nail that is used to set the anchor and has very low rust resistance. The metal hit anchor is available with a stainless steel nail that would be suitable for use in outdoor applications.
Read more about metal hit anchors.
Split Drive
Split drive anchors are only available in zinc plating and would not be suitable for use in outdoor applications or in applications where moisture is present.
Lag Shield
The lag shield is made from a zinc alloy zamac 5 that is rust resistant. It is suitable for use in outdoor applications only when the lag screw that is inserted into it for fastening is made from a stainless steel material.
Double Expansion Anchors
The double expansion anchor is made from a zinc alloy zamac 5 that is rust resistant and therefore suitable for outdoor applications. It is critical that the machine screw that is used with the double expansion anchor is manufactured from stainless steel.
Single Expansion
Single expansion anchors are made from a zinc alloy zamac 5 which provides rust resistance and is suitable for outdoor applications. It is critical that the machine screw that is inserted into the single expansion anchor is made from a stainless steel material.
Before using concrete anchors or fasteners in an outdoor application, it is imperative that the correct type of anchor is chosen. When using anchors in applications where moisture, salt or other chemicals are an issue, the concrete fastener must meet certain requirements and be rust resistant.
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Please remember with all fastening jobs to keep safety in mind. Always follow safety instructions on all tools, refer to manufacturer's installation
instructions when available and always remember to wear safety goggles!
Article written by: Michael Pistorino, Concrete Fastener Specialist