Fastening on Steel in Corrosive Environments

Hilti provides a range of faster, more reliable and efficient solutions for fastening on steel

Ideal for corrosive environments, such as the energy and industry sector.

When you think that your medium-to-large project may need as many as 100,000 fastenings to attach components to structural steel, a faster method for corrosion-resistant fastenings would seem long overdue.

With such volumes, design engineers and contractors working in corrosive environments – like oil & gas, petrochemical, and power & utilities projects – would welcome faster and more efficient ways of fastening components to structural steel. As an additional challenge, the components – such as grating, strut, conduit, cable trays, pipes, electrical boxes, supports for instrumentation panels, etc. – and the fasteners are often exposed to harsh weather, pollution and coastal environments, therefore requiring corrosion protection.

The structural steel may be hot-dip galvanized or coated with paint to help provide adequate corrosion protection depending on the specific environment. However, when fastening components, design engineers and contractors must ensure the corrosion protection of the structural steel is not compromised. The traditional fastening methods used under these conditions include welding, through-bolting and clamping. In this editorial we will compare these with the Hilti methods for fastening on steel and show how Hilti can help save you both time and money.

What is corrosion?

Corrosion is the physicochemical interaction between a metal and its environment, which results in changes in the metal’s properties and may lead to significant functional impairment of the metal, the environment, or the technical system of which they form a part (see ISO 8044:2010).

In construction and engineering corrosion may have a major impact on structures and fastenings made of metals such as carbon steel, stainless steel, zinc, copper and aluminum. It is estimated that roughly one fifth of the world’s annual steel production is to replace parts damaged by corrosion. While this amounts to a considerable economic loss, a greater concern is the safety risks, where corrosion may lead to failure in a fastening system.

Welding

Preparing the coated steel using an angle grinder

Prepare surface

Time consuming preparation of the coated steel e.g. with an angle grinder
Creates a lot of sparks, which can be a hazard

Weld channel to steel structure

An experienced and certified welder is required
External power supply required, which can be difficult on some jobsites
May require a hot work permit and, on some sites, a dedicated fire watch
Can be weather-dependent

Clean and repaint area

Need to wait until the welded area has cooled down before painting
Multi-layer painting common in the Oil and Gas industry can take 3 to 6 days, including drying time, meaning expensive and time-consuming rework

Through bolting

Multi-step drilling

Drilling process can be time-consuming depending on the thickness and hardness of the steel
Steel exposed from the drilling must be properly coated to avoid corrosion

Secure the channel in place

Access to both sides is needed
Installer needs to work with small parts such as nuts, washers and bolts that may get dropped or lost

Clamping

Positioning the clamp and channel where access to both sides of the structural steel is needed

Position the clamp and channel

Limited in direction of attachment of the component since clamps require a specific orientation relative to the structural steel
Access to both sides of structural steel is needed
Very high material costs, especially for corrosion-resistant clamps in hot-dip galvanized or stainless steel

Complete the fastening

Proper tightening is necessary, however over-torqueing may cause damage to the coating of the steel
If clamp is exposed to vibration then periodic maintenance might be required

Innovative Hilti methods for fastening on steel

Hilti offers a variety of methods customized to various corrosive environments that help reduce or eliminate the drawbacks of traditional methods. Depending on the corrosive environment and type and thickness of the base material, Hilti offers three different fastening options. These solutions help maintain the corrosion resistance of the structural steel and the connection to the non-structural components.

Three fast and reliable ways for fastening on steel

Sharp tip fastening

A fastening technology where a sharp tip stainless steel fastener is driven by a powder-actuated tool into the base material, creating a high-quality connection.

Suitable for high-frequency fastening where the fastening can be completed in a few seconds

Stainless steel fasteners for mildly-corrosive environments where penetration through base steel is acceptable.

Watch the sharp tip video

Diagram of a cross-section of steel showing blunt tip fastening

X-BT blunt tip fastening

A revolutionary fastening technology where a blunt-tip stainless steel fastener with a smooth cylindrical or conical shank is driven by a powder-actuated or battery-powered tool into a pre-drilled hole in the base material, creating a high-quality connection.

No damage to the corrosion protection coating in non-through penetration applications
Fastenings in less than 2 minutes

Duplex stainless steel fasteners for highly-corrosive environments. Fiber reinforced polymer (FRP) / duplex stainless steel fasteners for mildly-corrosive environments.

Watch the blunt tip video

Diagram of a cross-section of steel showing blunt tip screw fastening

S-BT blunt tip screw fastening

A revolutionary fastening technology where a blunt-tip stainless steel fastener with a screw type shank is driven by a torque controlled screw driver into the pre-drilled hole in the base material creating a tapped connection.

No damage to the corrosion protection coating in non-through penetration applications
Fastenings in less than 2 minutes

Duplex stainless steel fasteners for highly-corrosive environments. Duplex coated carbon steel fasteners for mildly-corrosive environments.

Watch the blunt tip screw video

Advantages over traditional methods

Eliminates the need for base material preparation

Unlike welding or through bolting, Hilti fastening solutions do not require preparation of base material and re-work after the fastening is made. This makes the overall installation much faster, while providing reliable corrosion protection.

Skilled welder is not required

Hilti blunt tip fastening on steel can be completed by any trained operator and do not require a certified welder. Therefore, contractors can deploy welders to other critical applications where welding is an absolute must.

Only access to one side of the steel is needed

Unlike through bolting or clamping, Hilti fastening solutions do not require access to both sides of the steel. This further improves operator safety as there is no need to get fingers into tight spaces.

Weather independent and no external power source required

Hilti sharp tip solutions are for powder-actuated nailers, so can be used under all weather conditions. Cordless drills used for blunt tip solutions are built for tough jobsite conditions, so can be used in nearly all weathers. In addition, the cordless tools are powered by 22V Li-ion batteries so do not require a mains power supply.

Backed by testing and approval

Hilti provides comprehensive technical data for different thicknesses and strengths of base steel. This data is backed by International Codes Council’s Evaluation Service (ICC-ES) as well as industry approvals including, but not limited to, the American Bureau of Shipping (ABS). In addition, Hilti blunt tip screw fastening technology has been tested, and is approved for use, in aluminum base material.

Easy to check installation quality

Both Hilti sharp tip and blunt tip fasteners are easy to inspect after installation using a visual check or a check gauge.

No through penetration or damage to the back of the steel

With Hilti blunt tip technology, fastenings can be completed without damaging the corrosion protection coating, making it ideal for highly-corrosive environments.

Lower cost per fastening point

As shown in the chart below, Hilti blunt tip solutions can be 57-63% more cost effective compared to traditional methods in mildly corrosive environments. Using Hilti sharp tip solutions in mildly-corrosive environments can often provide even more cost benefits in terms of total installed cost per fastening.

For a project with 100,000 fastenings of strut/channel to coated steel, the benefits over welding can be ~ $1.9 M based on the assumptions below for material and labor costs.

Disclaimer
Cost / time are estimates, can vary significantly, and use the following assumptions:

– Number of strut: 1,000
– Type of fastening: strut to steel with 2 connections per strut
– Number of fastenings: 2,000
– Labor rate for skilled welder: $ 50/hour
– Labor rate for skilled tradesman other than welder: $ 40/hour

*While welds require electrode and energy, the example assumes that the material cost is negligible for welding
**Touch up time considered for through bolting and welding