Corrosion Prevention & Control (CPC) Fencing Knowledge Area  

By: Joseph C. Dean, P.E., and Steve Geusic, P.E., for the Director, Corrosion Policy & Oversight (D, CPO) [OUSD (AT& L)

Updated: 04-18-2018

 

INTRODUCTION

Although, the word "corrosion" is most often associated with "rust" and the oxidation of other metals, 10 U.S.C. § 2228 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.

DESCRIPTION

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 Planning Manual, and related guidance.

Fencing Design and Durability

Factors affecting fencing design and durability include:

  • Function-Security, safety, entry requirements, and boundary identification
  • Environmental severity and location specific corrosivity
  • Structural integrity of posts, fabric, supporting members, gates, etc.
  • Aesthetics – typically fencing must comply with an installations appearance plan. If a paint or coating is required, environmental severity and corrosion must be considered.

Section 1-10 of 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." In the area of Material Selection and Coatings (Section 1-10.1), "Local environments must be considered during the selection of material for the fencing components as well as the required coatings to provide protection against corrosion. Color polymer and other coatings on fencing fabric, fittings, framework, and gates must be applied to enhance visibility and provide greater corrosion resistance, especially in corrosive or salt laden environment."

"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 rain water running from one surface to another, or moisture from the air containing enough acid to cause it to act as an electrolyte.

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 2015), 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.

This problem affects fencing needed to secure military equipment, supplies, and buildings. Painted and galvanized-steel 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 [Department of Defense] 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, 2014). 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 paragraph 1-4.1 Content Guidance, 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 9223 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

  • Standard galvanized steel fencing meeting Unified Facilities Guide Specification (UFGS) 32-31-13, Chain Link Fences and Gates, as a control
  • Standard PVC-coated fencing meeting UFGS 32-31-13 as a control
  • Galvanized steel coated with fuse-bonded PVC powder coating- (green) (ASTM F668, Class 2b)
  • Stainless steel American Iron and Steel Institute (AISI) 304 alloy with 18% chromium and 8% nickel by weight
  • A proprietary 5% aluminum/95% zinc (by weight) coating metallurgically bonded to a core of ASTM A-817, Type III steel
  • Aluminum alloy 6061-T94
  • Aluminized steel (ASTM A-817, Type I)

Railings

  • Carbon steel mill finish A513 coated with a long oil primer performance comparable to Specification SSPC 25 and top-coated with a medium oil alkyd enamel Federal Specification Mil-E-15090) followed by an alkyd enamel top coat
  • Aluminum alloy 6063 mill finish and clear anodize pipe 30 minute anodized (Aluminum Association specification for anodized finishes AAM12C22A31)
  • Type 304 stainless steel pipe and #4 satin finish
  • Fiberglass Reinforced Plastic (FRP) square tube (0.125 in. wall)

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. It should be noted that ERDC-CERL is currently conducting a follow-on re-evaluation of the fencing materials placed into service and on exposure racks under Project F09–AR02. 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. Findings and recommendations will be revised and updated based upon the results of this re–evaluation.

Identifying the corrosive forces and employment of CPC design strategies include:

  • Identification of the appropriate ESC Zone
  • Selection of materials to prevent dissimilar metal corrosion
  • Use of protective coatings, isolators, & corrosion inhibitors
  • Consideration of alternate materials for components proximate to salt water and in areas of high environmental severity
  • Prevention of entrapment of water
  • Provision of appropriate grounding features (see paragraph 2-10, UFC 4-022-03)
  • Reinforcement for the fencing structure
  • Consultation with subject matter experts and stakeholders when appropriate

In an effort to balance the realities of the severe corrosive environment in the Marianas with available fencing materials, Paragraph G2040.1, Fences and Gates, of 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 A-491, 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:

  • Fabric (e.g. welded wire, chain link, PVC coated, etc.)
  • Selvage
  • Posts (e.g. steel, composite, concrete)
  • Rails (top and bottom)
  • Barbed Wire and Barbed Tape
  • Outrigger and Barbed Wire Arm
  • Tension Wire (Top and Bottom)
  • Sleeves
  • Hot Ring
  • Truss Rod
  • Line Posts
  • Stretcher Bars
  • Tie Wires
  • Tension Bar and Clip
  • Concrete Footings
  • Rails
  • Braces
  • Gates (e.g. gate posts, hardware, and accessories)
  • Turnstiles
  • Grounding (See UFGS 32 31 13, 32 31 26, and 32 31 13.53 for details)
  • Reinforcement (e.g. anchors, welded brass rails, cabling, turnbuckles, threaded rods, anchor plates, etc.)
  • Miscellaneous Hardware (e.g. pad locks)

Two examples of fencing drawing details are shown in Figures 1 and 2. Paragraph 1-5.3 of 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), USACE Protective Design Center.

Figure 1. Standard Details for Chain–Link Security Fence (FE7), USACE Protective Design Center.

Deadman Anchor Detail (Source: UFC 4-022-03, 1 October 2013, Figure 2-6)

Figure 2. Deadman Anchor Detail (Source: UFC 4-022-03, 1 October 2013, Figure 2-6).

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 Chain Links Fences and Gates, Part 2 paragraph 2.1 Fence Fabric:

NOTE:  In salt-laden or corrosive industrial atmosphere, either Class 2 fabric with 610 grams 2.0 ounces of zinc coating per square meter foot or Type I, aluminum-coated fabric, will be specified. In other areas, Class 1 with 370 grams 1.2 ounces of zinc coating per square meter foot or Type I will be specified. Class 2b polyvinyl chloride-coated steel fabric may be specified for other than security purposes when esthetics is of prime importance and the additional cost is justified."

Although an increase in zinc coating will help extend the service life of galvanized steel fencing, recent studies have shown that PVC coated fabrics and aluminum alloys are a better choice in salt laden environments. Another example can be found in paragraph 2.2.2 Posts [,Rails] and Braces in UFGS 32 13 13 Chain Link Fences and Gates:

NOTE:  Grade A pipe which has the heavier zinc-coated interior may be desired in some coastal regions located in highly corrosive salt-laden environments to prevent rust caused by condensation inside the pipe. Grade A or Grade B pipe may be used in inland and desert areas, provided Grade B pipe meets the salt spray test."

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.

Lessons Learned And Input From The Field

  • Materials and systems used in fencing have to 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

  • 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

  • Typically, a zinc coating (galvanizing) is used unless there is a specific requirement such as the use of PVC in high visibility areas or for highly corrosive environments

  • 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

Summary

Galvanized steel fencing is typically the lowest first cost option and is specified most often as the minimum requirements in guide specifications (UFGS 32-31-13 Chain Link Fences and Gates). Galvanized steel normally provides adequate corrosion protection and a suitable service life for fencing and components in less severe corrosive environments.

In more severe corrosive environments, the service life of 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
  • Use alternate materials and coatings
    • Fused-bonded PVC and standard PVC coated – both perform 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.

    • Aluminized (aluminum coated steel) fencing components, including fence fabric in accordance with ASTM A-491, post, rails, braces and gates in accordance with ASTM B211-03

  • For railings, both Anodized Aluminum alloy 6063 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 aluminized 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. Materials choices need to balance resistance to corrosion with resistance to mechanical degradation and aesthetics.

Obtaining Fencing Subject Matter Expert (Sme) Assistance

"Establishing the design criteria for security and antiterrorism is not something that can be done effectively by one person. It requires a team… Based on local considerations, there may be others who should be consulted for input into the design criteria" (paragraph 1-5.3, UFC 4-022-03). Design criteria must be selected based upon the requirement and the environmental conditions that exist at the facility location. (See the Corrosion Toolbox).

Fencing and the associated security and anti-terrorism aspects cross multi-discipline areas which may require more persistence by designers and maintainers in obtaining necessary insights from SMEs. The SMEs can assist with the translation of local conditions into the interdisciplinary solutions that provide immediate and long-term benefits to the installation and its SRM bottom line costs. Typical consulting services provided by the SMEs include:

  • Multi-discipline coordination and understanding
  • Materials analysis and selection
  • Problem assessment
  • Failure analysis
  • Environmental Severity impacts
  • System and material selection
  • Review and assessment of contractor deliverables
  • Quality evaluation and assurance
  • System design
  • Sustainment, Restoration and Modernization (SRM) analysis and recommendations (system inspection and testing assistance)
  • Hazards analysis
  • Assessment of the sustainability and durability of new technologies
  • Process analysis
  • Anti-terrorism threat analysis and protection technologies

Relevant Codes and Standards

Criteria on the WBDG are generally based on industry standards. An industry standard is an established norm or requirement about technical systems, usually presented in the form of a formal document. It establishes uniform engineering or technical criteria, methods, processes and practices. Industry Standards can also be found in the form of reference specifications. The standards referenced in criteria are usually written and maintained by Standards Organizations (see also WBDG Code Taxonomy).

Department of Defense

Unified Facilities Criteria (UFC)

Unified Facilities Guide Specifications (UFGS)

Industry Organizations

ASTM International

  • ASTM A116 Standard Specification for Metallic-Coated, Steel-Woven Wire Fence Fabric
  • ASTM A153 Standard Specification for Zinc Coating (Hot Dip) on Iron and Steel Hardware
  • ASTM A702 Standard Specification for Steel Fence Posts, Hot Wrought
  • ASTM A491 Standard Specification for Aluminum-Coated Steel Chain-link Fence Fabric
  • ASTM F2611 Standard Guide for Design and Construction of Chain Link Fencing Materials Used for High Security Applications
  • ASTM F1712 Standard Specification for Steel Chain Link Fencing Materials Used for High Security Applications
  • ASTM A121 Standard Specification for Metallic-Coated Carbon Steel Barbed Wire
  • ASTM F1910 Standard Specification for Long Barbed Tape Obstacles
  • ASTM 1911 Standard Practice for Installation of Barbed Tape
  • ASTM 1665 Standard Specification for Polyvinyl Chloride (PVC) and Other Conforming Organic Polymer– Coated Steel Barbed Wire Used with Chain-Link Fence
  • ASTM F1043 Standard Specification for Strength and Protective Coatings on Steel Industrial Fence Framework
  • ASTM A-702 Standard Specification for Steel Fence Posts and Assemblies, Hot Wrought
  • ASTM F1083 Standard Specification for Pipe, Steel, Hot Dipped Zinc– Coated (Galvanized) Welded, for Fence Structures
  • ASTM A500 Standard Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes
  • ASTM F2453 Standard Specification for Welded Wire Mesh Fence Fabric (Metallic-coated or Polymer Coated) for Meshes of 6 in2 [3871mm2] or Less, in Panels or Rolls, with Uniform Meshes
  • ASTM 2780 Standard Guide for Design and Construction of Expanded Metal Security Fences and Barriers
  • ASTM F2548 Standard Specification for Expanded Metal Fence Systems for Security Purposes
  • ASTM F900 Standard Specification for Industrial and Commercial Steel Swing Gates
  • ASTM F1184 Standard Specification for Industrial and Commercial Horizontal Slide Gates
  • ASTM F2200 Standard Specification for Automated Vehicular Gate Construction
  • ASTM A1023/A1023M Standard Specification for Stranded Carbon Steel Wire Ropes for General Purpose
  • ASTM F-626 Standard Specification for Fence Fittings

Additional Resources

WBDG

References

Assistance

Obtaining SME Assistance for DoD Installations