When thinking about installing fencing, you should first consider the environment in which it will be placed.
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Is it near the coast?
Is it exposed to extreme changes in temperature?
Will it be located in a wet or humid environment?
Will it be in close proximity to corrosive chemicals, etc.?
Identifying these factors will help you determine the best type of fence product and coating for your needs.
GBW - Galvanized Before Weld
Let&#;s start with the basic low-cost GBW welded wire fence. This product is available in a wide variety of styles and sizes for lots of different applications. This is what most &#;Big Box&#; stores sell.
The good news? It is inexpensive.
The bad news? It has a shorter life because it is more susceptible to rust and corrosion.
The reason? The wire is welded before it is galvanized. The welding process can &#;burn-off&#; the zinc on the weld points. This makes the wire more vulnerable to rust and corrosion.
The initial strength and gauge of the GBW wire are the same as GAW and VC. But the finish is not nearly as durable resulting in a shorter usable lifespan.
If price rather than quality is the most important factor, then GBW might be a good choice for you.
GAW - Galvanized After Weld
GAW welded wire is dipped in molten zinc after being welded or woven. The wire is fully encased in zinc for greater protection and longer life. This is especially important if the fence is to be installed in coastal areas, and if rust and corrosion are primary concerns.
The good news? Extended lifetime
The bad news? It is slightly more expensive than generic GBW meshes.
The reason? After the wire mesh is welded or woven, the finished product is drawn through a bath of molten zinc. The wires are thoroughly galvanized. And most importantly the welded joints are completely covered and protected from the elements. Moisture, which tends to collect in these areas, is prevented from contacting the underlying wire.
If quality and long life are the most important factors in how you will make your decision, GAW is a great choice. The thick galvanization present on the wires adds years of life to the fence. GAW fencing materials will long outlast commonly available GBW products. You have to look harder to find GAW wire fencing materials, but your search will be rewarded with years of service. Avoid the needless expense and hassle of frequent replacement. Buy a product that will last!
VC - Vinyl Coated
VC welded wire has been coated with a layer of PVC after the mesh is welded up. The vinyl covers the mesh and provides strong protection against the element.
The good news? Extended lifetime and attractive appearance
The "bad" news? It can be more expensive than GBW and GAW products.
The reason? The addition of the PVC coating adds an impervious barrier, protecting the wire from Mother Nature's harshest elements. The protected wire will not rust as quickly.
If you want a product that is not only attractive but is also able to withstand environmental stressors, VC welded wire mesh is the perfect one to use. Black mesh becomes virtually invisible.
Note: It is very important to know what to look for when considering VC wire fencing materials. The best possible protection and longest life expectancy are offered by a product that is vinyl coated over GAW wire mesh. You will have rugged double protection. You will not be disappointed.
SS - Stainless Steel
SS welded wire fences provide the greatest level of protection and long life in any environment. The product is more expensive up front but can save lots of money and time in the long run because the fence will not need to be repaired or replaced. Stainless Steel wire needs no additional coating because it will last for years and years in practically any environment.
The good news? Very long life with little maintenance required
The "bad" news? Yep, It's pricier.
The reason? Stainless Steel is a more expensive material. But in certain applications, its longevity will ultimately prove less expensive.
Did you know there are a great many varieties of wire mesh fencing materials available to you?
Do you have some new ideas or questions about what you would like to use on your next project?
by Joseph C. Dean, P.E., and Steve Geusic, P.E., for the Director, Corrosion Policy & Oversight (DASD) [Materiel Readiness]
Updated: 12-10-
Although, the word "corrosion" is most often associated with "rust" and the oxidation of other metals, 10 U.S.C. § defines corrosion as, "the deterioration of a material or its properties due to a reaction of that material with its chemical environment." It is inclusive of the deterioration of all materials, which can be caused through sun exposure, mold and mildew, wind, and other environmental factors.
Facilities components affected by corrosion include, but are not limited to, pipelines, fuel tanks, pavements and bridges, roofs, transformers, switchgear, electrical boxes, heating, ventilation and air conditioning (HVAC) equipment, water towers, fire hydrants, motors, compressors, wharfs and piers, boilers, ladders, stairways, wash racks, fire sprinkler systems, airfield pavements, steam lines and facilities, tankage, petroleum, water distribution lines, as well as fencing, connectors and associated fasteners. Corrosion effects often remain unseen or unnoticed until failure occurs.
Fencing and the associated components (e.g., gates, posts, fabric, extension arms, locks, turn stiles, connectors, fasteners, etc.) provide some of the most visible features at an installation and can become very unsightly due to corrosion. While serving an essential role in providing security to valuable assets, fencing is a costly facility category to sustain. Once installed, it is often left to the ravages of the environment and time without follow-on care. Material degradation with the associated specter of reduced security capability and limited options for fencing maintenance (without replacement) require diligence on the part of the facility manager.
Note that this Fencing Knowledge Page is focused on the prevention and management of corrosion for these components. It is not intended to address the security component selection and sustainment of locks, surveillance cameras and the other specialized features addressed in UFC 4-022-03 Security Fences and Gates, UFC 4-020-01 DoD Security Engineering Facilities Planning Manual, and related guidance.
Factors affecting fencing design and durability include:
A recent Life Cycle Cost Analysis (LCCA) was conducted through a Department of Defense (DoD) project to evaluate the long-term performance of fencing components in corrosive environments. This LCCA evaluated alternative types of chain-link fence fabric as well as posts and rail material types. The results for fence fabric showed that the Zinc-coated Steel fabric with 1.2 oz/SF zinc coating (ASTM A392, Class 1), and the Aluminum-coated steel fabric (ASTM A491) were the 2 lowest cost alternatives with respect to initial construction costs. However, over a 30&#;year analysis period, the 2 lowest cost alternatives were shown to be Aluminum-coated steel fabric and PVC-coated over zinc-coated steel fabric (ASTM F668, Class 2b). With respect to posts and rails, the LCCA results showed that the Class 2 Aluminum Pipe (ASTM B429, alloy -T6) and the Class 1 Grade B Steel Pipe (ASTM F/F) were the 2 lowest cost alternatives with respect to initial construction costs. Over a 30&#;year analysis period, the 2 lowest cost alternatives were shown to be Class 2 Aluminum Pipe and PVC-coated over zinc-coated steel pipe ("heavy mil", 10 mils coating).
Based on the results of the LCCA, the DoD design and construction criteria have been revised to require either Aluminum-coated steel fabric or PVC coating over zinc-coated steel fabric; and either Class 2 Aluminum Pipe or PVC coating over zinc-coated steel pipe ("heavy mil", 10 mils coating) in corrosive environments and high humidity locations.
UFC 4-022-03 requires that "design strategies for installation security structures and equipment must consider corrosion prevention and control (CPC) preservation techniques for long-term maintainability throughout their life cycle. Trade-off decisions involving cost, useful service life, and effectiveness must address corrosion prevention and mitigation." The UFC also states that, "Local [corrosive] environments must be considered during the selection of material for the fencing components as well as the required coatings to provide protection against corrosion." Upgrade fencing components at exterior locations where microenvironmental factors may create a locally corrosive environment regardless of ESC (for example, waterfront environments, industrial emissions, deicing salt application, and possible chemical splash/spillage). In addition, upgrade fence materials utilized in interior applications when in a corrosion prone environment (examples include pools and aquatic training facilities). See UFC 1-200-01 for additional upgrade considerations due to corrosion prone environments. Utilize either aluminum-coated steel fabric and aluminum framework or provide polymer coatings on zinc-coated fencing fabric, fittings, framework, and gates to provide greater corrosion resistance, especially in corrosive environments defined as project locations with Environmental Severity Classifications (ESC) of C3 thru C5 and high humidity locations. High humidity locations are those in ASHRAE climate zones 0A, 1A, 2A, 3A, 3C, 4C, and 5C (as identified in ASHRAE 90.1). See UFC 1-200-01 for determination of ESC for project locations. Areas prone to metal loss caused by blowing sand also require polymer coatings on fence components; examples of these include desert locations and project locations prone to high winds in a coastal area. DoD research has shown bare zinc-coated steel to have lower first costs but significantly higher life-cycle costs in corrosive environments; when using bare zinc-coated steel in ESC C1 and C2 locations, use a thicker coating for extended service life."
UFC 4-022-03 states "Coating on any fasteners or ties must be electrolytically compatible with fencing fabric to inhibit corrosion. All security fence fittings must be electrolytically compatible with all fence components. One of the most important corrosion issues is the chemical reaction between dissimilar metals. When dissimilar metals are in contact with one another in the presence of an electrolyte, galvanic action occurs, resulting in their deterioration. The electrolyte may be rainwater running from one surface to another, or moisture from the air containing enough acid to cause it to act as an electrolyte." When the use of dissimilar metals is unavoidable, minimize or prevent the galvanic corrosion by isolating the metals with an inert material or coating, sealing openings which would allow moisture intrusion, or applying a corrosion-inhibiting paste or compound to the interacting surfaces. An example of the proper application of dissimilar metals is the use of stainless steel fasteners with aluminum components, in lieu of using ferrous-based fasteners. Additional examples of solutions for dissimilar metals are included in UFC 1-200-01.
The Construction Engineering Research Laboratory (CERL), U.S. Army Corps of Engineers (USACE) Engineer Research and Development Center (ERDC) Project F09-AR02 Final Report, Demonstration and Validation of Materials for Corrosion-Resistant Fencing and Guard Railings in Aggressive Climates (October ) , stated that, "even metals with higher quality coatings, such as PVC, can corrode in these ["aggressive"] environments. Standard galvanized steel chain-link fencing, including products coated with polyvinyl chloride (PVC), can severely corrode in as little as 5 years in coastal locations where the atmosphere is warm, humid, and infused with chlorides.
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This problem affects fencing needed to secure military equipment, supplies, and buildings. Painted and zinc-coated safety railings also can severely corrode in those environments, creating personal-safety hazards." The Report also emphasizes that "traditional fence and railing materials last 5&#;7 years in a corrosion-prone environment before replacement is required adding to maintenance costs. The key to lowest cost is proper material selection." The UFC 3-701-01 DoD Facilities Pricing Guide indicates a 26&#;year service life for Boundary Fencing and Walls, and Security Fencing for use in Military Construction (MILCON) Projects.
"Degradation of DoD fencing generally occurs as a result of corrosion of carbon steel. Corrosion factors affecting fencing include temperature, proximity to salt water, salt fall, high humidity, wind, sand erosion, and ultraviolet (UV) exposure," according to the Vision Point Systems Study "Corrosion Factors in DoD Facilities," (October 24, ) . From an Operations and Maintenance (O&M) perspective, the constructed facility that provides the least effort to maintain and meets performance, security, and appearance objectives is preferable. In more severe environments, higher corrosion-resistant fencing materials and coatings can reduce O&M costs. Often corrosion damaged fencing is replaced with the same materials adding to a negative life cycle impact (Project F09-AR02 ).
UFC 1-300-02 UFGS Format Standard, requires that designers "provide bracketed or tailored options, and Notes to the Designer, in the UFGS sections when the selection of a material, component, or system for corrosion prevention, life cycle cost effectiveness, or durability depends on the location, application, conditions, or atmospheric and chemical environment. In the notes, provide direction on identifying and selecting those variables." It also states that "ISO and Environmental Severity Classification (ESC) factors, [should be used] to help specify when to use materials, coatings, and other design elements in a given project location or atmospheric environment. Additionally, provide direction on what item to use based on other relative criteria such as soil corrosivity, ultraviolet exposure, solar radiation, biological, or other factors causing deterioration of a material or its properties because of a reaction of that material with its chemical environment."
Ideally all components of the fencing "system" should address corrosion vulnerability and durability. According to the findings in the Project Report for F09-AR02 , "results indicate that using corrosion-resistant materials could reduce the life-cycle costs of fences and railings by 62 to 80%. The return on investment (ROI) ratio for using fuse-bonded fencing and anodized aluminum railings was calculated at 6.13; and the ROI for using FRP composite railings instead of anodized aluminum was 5.75."
In the F09-AR02 Report , poles, railings, and wire (9 gauge) were field tested and evaluated at three locations with various materials and coatings:
Fence Types Tested
Railings Tested
NOTE: The fence components other than poles, wire, and railings were not addressed in the F09-AR02 Project research. However, those components must also be considered and are equally as impacted. Material selection of components such as fasteners, straps, connectors, end caps, etc., are showing severe corrosion compared to the fence fabric evaluated in the Project. Material selection of these items is critical for system longevity and low maintenance. It is recommended that further research be conducted into these areas.
Identifying the corrosive forces and employment of CPC design strategies include:
In an effort to balance the realities of the severe corrosive environment in the Marianas with available fencing materials, the Marianas Navy and Marine Corps Design and Construction Standards (MDACS) requires that:
"Perimeter fences shall be aluminized (aluminum-coated steel) fencing components, including fence fabric in accordance with ASTM A491, post, rails, braces and gates in accordance with ASTM B211-03 and verified by the [Contracting Officer's Representative] COR for appropriate locations. Polyvinyl chloride (PVC) coatings shall be in color and a minimum thickness of 2 mm (0.10 inches). Verify if top and/or bottom tension wires and top and/or bottom rails are to be provided; where tying into an existing fence, match the fencing system.
Provide an ornamental or decorative fence of aluminized (aluminum coated) steel with a colored vinyl or other approved coating for recreational or housing fences as verified and approved by the COR. Polyvinyl chloride (PVC) coatings shall be [_____] in color and a minimum thickness of 2 mm (0.10 inches). An optional decorative fence type is hot-dipped galvanized steel with a colored vinyl coating, which shall be verified with the COR.
Perimeter and security fences shall conform to the applicable base installation appearance plan as appropriate and be reviewed by the [Public Affairs Officer] PAO or Base Security officer."
Design components for fencing may include:
Two examples of fencing drawing details are shown in Figures 1 and 2. UFC 4-022-03 Security Fences and Gates emphasizes that the design for fencing projects include more than security and antiterrorism requirements.
Figure 1. Standard Details for Chain-Link Security Fence (FE7)
Source: USACE Protective Design Center
Figure 2. Deadman Anchor Detail
Source: UFC 4-022-03
Each of the criteria documents provide material selection guidance for both corrosive and less corrosive environments. An example of this guidance occurs in UFGS 32 31 13.53 High-Security Fences (Chain Link And Ornamental) and Gates:
NOTE: Use either aluminum-coated steel fabric or Class 2b (fused and adhered) PVC-coated over zinc-coated steel fabric for project locations with Environmental Severity Classifications (ESC) C3 thru C5; ESC C1 and C2 locations can use other options. Use Class 2b PVC-coated over zinc-coated steel fabric when fabric is being buried in soils and in areas where coatings are prone to abrasion from blowing sand. It should be noted that DoD research has shown zinc-coated (galvanized) fabric steel to have lower first costs but significantly higher life-cycle costs in corrosive environments; when using zinc-coated steel in ESC C1 and C2 locations, use Class 2 fabric with 2.0 ounces per square foot of zinc coating for extended service life. See UFC 1-200-01 and the Corrosion Toolbox for determination of ESC for project locations."
Due to recent studies having shown that PVC coated fabrics and aluminum alloys are a better choice in corrosive environments, the fencing-related UFGS's require use of PVC-coated over zinc-coated or aluminum-coated steel fabrics, in combination with either PVC-coated zinc-coated steel or Class 2 aluminum rails and posts in these areas. Where aluminum-coated steel fabric is used; posts must be constructed of aluminum piping. Examples related to posts and railings can be found in UFGS 32 31 13 Chain Link Fences and Gates:
NOTE: Use either Class 2 aluminum pipe or include PVC coating on zinc-coated steel pipe posts and railings in locations with ESC C3 thru C5, and high humidity locations. When specifying steel pipe posts, use Grade A pipe which has the heavier zinc-coated interior in locations with ESC C3 thru C5, and high humidity locations. Also use Grade A steel pipe where steel posts are buried in direct contact with soil, regardless of the ESC of the project location. Grade A or Grade B steel pipe may be used in locations with ESC C1 or C2 and in low humidity locations, provided Grade B pipe meets the salt spray test. High humidity locations are those in ASHRAE climate zones 0A, 1A, 2A, 3A, 3C, 4C, and 5C (as identified in ASHRAE 90.1). See UFC 1-200-01 and the Corrosion Toolbox for determination of ESC for project locations. Where aluminum-coated steel fabric is used, use Class 2 aluminum pipe. In areas where coatings are prone to abrasion from blowing sand, use PVC coating on zinc-coated steel pipe posts and railings.
It is recommended that the designer carefully review each criteria document to ensure that the appropriate materials are selected and placed in service. Submittals may include shop drawings, product data, samples, test reports, certificates, manufacturer's instructions, and operation and maintenance data.
See the sections at the end of this knowledge page for fencing specific criteria and standards for decision-making analysis and design guidance. Understanding Corrosion Science and Environmental Severity impacts as it affects fencing design and materials selection will help the designer make decisions that are life cycle cost effective and more durable.
Materials and systems used in fencing must adhere to certain minimum industry exposure testing standards, such as moisture, uV, and salt spray testing (ASTM G152-ASTM G155)
Fence posts are normally encased in concrete and are not in direct ground contact. In high corrosivity soils there are concrete mix options to reduce concrete permeability
Where aluminum posts are used with concrete footings, design such that post is isolated from direct contact with the concrete. This may include incorporating an aluminum sleeve, or designing as an insert or "frangible" connection.
Post caps get knocked off which allows rain to get down inside the post where it becomes trapped, causing internal corrosion weakening the fence post
Fence fabric is usually the first component to degrade and need maintenance or replacement
Length of fencing system can have a significant effect on cost benefits and choice of corrosion protection
Components with a standard zinc coating (galvanizing) can corrode rapidly when installed in corrosive environments; thus, the most appropriate fabrics are either aluminum-coated steel, or PVC-coating over zinc-coated or aluminum-coated steel, and the most appropriate framing members are either Class 2 aluminum piping or PVC-coating over zinc-coated steel piping
Meeting security requirements is the number one design factor. The gauge of the fencing is critical
Local suppliers generally know what works for that location. However, this does not ensure it will be provided in your project unless it is specified
In the past, zinc-coated (galvanized) steel fencing was specified most often as the minimum requirements in guide specifications (UFGS 32 31 13 Chain Link Fences and Gates) due to being the lowest first cost option. While zinc-coated steel provides adequate corrosion protection and a suitable service life for fencing and components in less severe corrosive environments (those being defined as locations having an ESC of C1 or C2), fencing materials must be upgraded in corrosive environments defined as having ESC of C3 thru C5. The corrosion-related upgrades to ensure an extended service life include requiring either aluminum-coated steel fabric or PVC-coating over zinc-coated steel fabric; the upgrades for fence framework components include requiring either Class 2 aluminum or PVC-coating over zinc-coated steel posts and railings.
In more severe corrosive environments, the service life of zinc-coated (galvanized) steel fencing is drastically reduced and enhanced corrosion protection should be employed by designers. Designers should evaluate the environmental severity of the installation and the microenvironment at the site for both atmospheric and soil corrosivity and employ additional corrosion resistant measures as appropriate. Some options available include:
Increase gauge of fencing and components
Increase thickness of zinc coating
Ensure material compatibility of components and fasteners
Fused and adhered PVC coating over zinc-coated steel (ASTM F668, Class 2b)&#;recent studies have shown this fabric to have the lowest life cycle cost and performs very well except where the PVC coating is damaged or at cut ends that are not protected. In these areas corrosion will eventually propagate further along the material and cause the PVC coating to separate from the core material, which can become aesthetically unacceptable and degrade substrate material performance.
Aluminum-coated steel (aluminized) fencing components, including fence fabric in accordance with ASTM A491, post, rails, braces and gates in accordance with ASTM B211-03
For railings, PVC-coating over zinc-coated steel, Anodized Aluminum alloy and FRP perform very well in corrosive environments. However, in high-intensity UV exposure, FRP may see discoloration and UV degradation. Use UV inhibitors and coatings and stainless steel A316 fasteners.
Note that aesthetics is often a primary concern for many fencing applications. Some materials, such as stainless steel and aluminum-coated steel, may produce acceptable levels of corrosion protection and resulting section loss but may experience severe discoloration from surface oxidation.
"Mechanical Degradation" could include fatigue, wear, and structural overload. Material choices need to balance resistance to corrosion with resistance to mechanical degradation and aesthetics.
Unified Facilities Criteria (UFC)
Unified Facilities Guide Specifications (UFGS)
ASTM International
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