The document discusses better fasteners for building construction. It notes that fasteners are a critical detail that connect larger building components. Specifying the right fasteners is important for project success as they must withstand loads and resist corrosion. The document outlines various types of corrosion that can affect fasteners, including rusting, galvanic corrosion caused by dissimilar metals, and hydrogen-assisted stress corrosion cracking (HASCC). HASCC is an invisible type of corrosion that causes fasteners to suddenly fail without visible signs of deterioration. The document emphasizes the importance of specifying corrosion-resistant fasteners.

1. Better Buildings from
Better Fasteners
Gregg Melvin, Elco Construction Products
Session (WE08)
Wednesday, June 17, 2009

2. AIA Credits
Hanley Wood is a Registered Provider with The American Institute of
Architects Continuing Education Systems. Credit earned on completion of this
program will be reported to CES Records for AIA members. Certificates of
Completion for non-AIA members available on request.
This program is registered with the AIA/CES for continuing professional
education. As such, it does not include content that may be deemed or
construed to be an approval or endorsement by the AIA of any material of
construction or any method or manner of handling, using, distributing, or
dealing in any material or product. Questions related to specific materials,
methods, and services will be addressed at the conclusion of this presentation.

3. CEN Credits
This program is a registered educational program with the Construction
Specifications Institute of Alexandria, VA. The content within this program is not
created or endorsed by CSI nor should the content be construed as an approval of
any product, building method, or service. Information on the specific content can
be addressed at the conclusion of this program, by the Registered Provider.
Credit earned for completing this program will automatically be submitted to the
CSI CEN. Completion certificates can be obtained by contacting the Provider
directly.
This logo and statement identify Provider programs registered with the CSI CEN
and are limited to the educational program content.

4. Copyrighted Materials
This presentation is protected by US and
international copyright laws. Reproduction,
distribution, display, and use of the
presentation without written permission of
owner is prohibited.
© 2009 Elco Construction Products

5. Learning Objectives
1. Identify situations requiring A/E to specify fasteners
instead of leaving product selection to contractor or
supplier.
2. Learn techniques for reducing fastener damage due to
rust and galvanic corrosion.
3. Be able to explain causes of hydrogen embrittlement
and HASCC.
4. Be able to specify high performance fasteners that are
HASCC resistant.
5. Explain the role of fasteners in building sustainability.

6. For want of a fastener…
“For want of a nail, the shoe was lost,
For want of a shoe, the horse was lost,
For want of a horse, the rider was lost.”
This old rhyme about a battle being lost
due to one missing nail is a parable
about making sure of the details.
Yet it’s specifically about fasteners,
because they are a particular kind
of detail – a small thing that
connects together larger and
more important things.
Compared to the horse
and even the shoe, the
fastener is small. Yet
without it…
“God is in the details.”
Mies van der Rohe

7. Your reputation hangs on
specifying the right fasteners.
Fastener specification are Standard types and grades of
critical to project success.
fasteners are sufficient in many
construction applications. In these
instances, fastener selection can
usually be based upon industry
standards, building code
requirements, and design loads.
It may even be acceptable in some
cases to leave fastener selection to the
discretion of contractors or building
The Petronas Towers in Kuala
Lumpur, the world’s tallest building
product fabricators, allowing them to
when constructed, required careful select fasteners based on cost,
engineering to assure that the
millions of fasteners used to install convenience, and trade practices.
cladding would not be the
installation’s weakest link.

8. Your reputation hangs on
specifying the right fasteners.
Fastener specification are
critical to project success.
At other times, however,
fastener selection can be one of
the most crucial aspects of
building design.
Professional judgment is required
to specify fasteners that:
Perform as intended
Are dependable and economical
The Petronas Towers in Kuala
Lumpur, the world’s tallest building Last the life of the building
when constructed, required careful
engineering to assure that the
millions of fasteners used to install
cladding would not be the
installation’s weakest link.

9. A big job for such a small part
Factors effecting fastener performance include:
Structural capacity and safety factor.
Static and dynamic load resistance.
Pull-out and pull-over resistance.
Shear resistance of fastener and attached materials.
Corrosion resistance in conditions of use.
Seal against liquid or gas leakage (if required).
Constructability, practicality, and inspectability.
Compatibility with design intent and aesthetics.
Removability, or other special requirements.
Service life exceeds that of attached materials.
Specifying fasteners is part of designing safe, durable, and
practical connections between building components.

10. HASCC
A “Continuing” Threat to Fasteners
HASCC = Hydrogen-Assisted Stress
Corrosion Cracking.
HASCC has only been identified as a
fastener failure mechanism within the
past few decades.
Since then, “Best Industry Practices”
have changed to protect fasteners
against HASCC.

11. VISIBLE CORROSION
Before considering HASCC, let’s review
some basics of ordinary fastener corrosion:
Oxidation (Rusting)
Galvanic Corrosion

12. Must it Rust?
Most architectural fasteners are made from grades or alloys of steel that will
react with oxygen to create ferrous oxide, commonly know as rust. Rust is a
type of corrosion that weakens and deteriorates steel. Rusting is
accelerated when steel is also exposed to moisture, especially if the
moisture contains chlorides (salts), a condition that is common in marine,
industrial, and urban atmospheres.
When designing steel-to-steel connections,
both the fasteners and the items being
joined must be protected against rusting.
Steel building panels, for example, can be
protected by using zinc galvanizing and a
high-performance coating.
As a general guideline, fasteners should
have greater corrosion resistance than Once rust starts, it can
items being joined so that fasteners do not spread rapidly to adjacent
become weakest link in connection. exposed steel surfaces.

13. Corrosion-Resistant Plating
Fasteners are often protected with metallic plating.
For example, zinc plating helps protect steel
against exposure to air and moisture and provide a
sacrificial, galvanic protection to steel.
Hot-dipped galvanizing is widely used for large
fasteners such as anchor bolts. The thick layer of
zinc deposited in this process clogs the threads of
smaller screws. On the other hand, thin coatings of
electroplated zinc applied to some screws do not
Plating is no longer provide sufficient corrosion resistance for exterior
considered acceptable or high performance fasteners.
protection for high Other types of metal plating, such as cadmium
performance fasteners. and hexavalent chromates, provide greater
corrosion-resistance than zinc. These materials are
decreasing in usage.
Specific plating such as noted above is
contraindicated for case-hardened fasteners and
others. We do not use HEX chromate or Cadmium
on our fasteners in our facilities.

14. Corrosion-Resistant Coatings
New types of anti-corrosion coatings can
be considered to protect high-
performance fasteners.
This type of coating is eco-friendly,
minimizing or eliminating the use of
heavy metals in fasteners.
In addition to corrosion resistance, the
coatings lubricate threads, making
fastener insertion and removal easier.
Easier removal is a big plus when doing
repairs, remodels, and retrofits.
Color can be used for product The coatings can be pigmented to color-
identification and aesthetic match other building materials or to
considerations.
simplify product identification.

15. Corrosion-Resistant Stainless Steel
300-series stainless steel provides even greater levels of
corrosion resistance. It should be considered for critical structural
connections and in locations with aggressive & or corrosive
environments.
Note: Even stainless steel often requires a coating for protection
against galvanic corrosion of materials they are attaching to or
together, as will be discussed later in this course.

16. Galvanic Corrosion
Galvanic corrosion occurs when dissimilar metals, such as
aluminum and steel, are in the presence of an electrolyte, an
electrically conductive medium, and form a galvanic cell.
These galvanic cells are similar to those in electric batteries. In
batteries, however, cells are sealed so galvanic reactions only occur
when the cells are part of a controlled electrical circuit.
The same reaction occurs in buildings when two pieces of metal form
an uncontrolled short circuit. It occurs because of the electro-
chemical relationship of the metals.

17. Galvanic Series
Metals conduct electricity because they have a tendency to give
up electrons easily. Some metals give up electrons more easily
than others. They can be listed in order of their potential to yield
electrons, in a table known as a Galvanic Series.
Cathode (Least Active)
More “noble” Gold
(protected and Silver
less corroded) Aluminum is more active
Stainless Steel
Bronze
(anodic) than steel or
Copper stainless steel. Where
Brass aluminum and steel form a
Nickel galvanic cell, aluminum
Lead
will corrode, sacrificing
Steel & Iron
Less “noble”
Aluminum
electrons that will deposit
(sacrificial
and more Zinc onto and protect the steel.
corroded) Magnesium
Anode (Most Active)

18. Galvanic Corrosion
This aluminum plate received two screws made from 300-series stainless steel,
a grade that is highly resistant to oxidation and rusting. It was then exposed to
1000 hours of salt-water spray that acted as an electrolyte to form a galvanic
cell between the aluminum plate and stainless steel fasteners. The screws
were them removed to allow examination of the plate.
Stainless Steel Stainless Steel Screw
Screw: The With Anti-Corrosion
aluminum sacrificed Coating: The coating
electrons to the prevent formation of a
steel. The surface galvanic cell and
of the aluminum is prevented corrosion of
visibly deteriorated. the aluminum plate.
Using ordinary steel fasteners in architectural aluminum elements (such as
windows, curtain walls, or wall cladding) can also create galvanic corrosion of the
aluminum, weakening the connection until it fails at well below design loads.
Avoid this problem by specifying fasteners with high-quality anti-corrosive
coatings.

19. Galvanic Corrosion
Dissimilar metal combinations are
common in construction. For example:
Aluminum framed glazing units and
cladding get attached to structural steel
framing using steel, self-drilling, self-
tapping screws.
Aluminum parts are often attached to
concrete or masonry with self-tapping
screws made of steel.
Even steel-to-steel connections can
involve dissimilar metals, if either of the
steel parts, or the fasteners joining
them, has been coated with zinc.
Thin veneers can be
attached with self-drilling
fasteners in the support
structure.

20. Galvanic Corrosion
It is difficult to prevent electrolytes from contact with fasteners.
Moisture can enter construction due to:
Rain or dew during Construction
Condensation inside a wall or roof
Leaks in building envelope
Water from building maintenance or operations
Plumbing failures
Flooding and spills
Perspiration from workers who installed the part
Air pollutants can make atmospheric moisture more conductive
If dissimilar metals are in contact, assume that an
electrolyte will also be in contact with the fasteners.
Specifying fasteners with adequate corrosion resistance protects
against catastrophic failure, loss of use, injury, death, and liability.

21. HASCC
The Invisible Corrosion
A secondary effect of the galvanic reaction
can also lead to fastener failures. Hydrogen,
a by-product of galvanic corrosion, can
weaken standard, hardened fasteners and
cause failures. It produces a type of
corrosion that is not readily apparent…until it
is too late.

22. A Case Study
20 years after installation, screws began snapping for no
apparent reason. The screws complied with building code
load requirements and industry manufacturing standards.
While they had been exposed to weather due to roof
damage, they were not visibly corroded. They simply
appeared to have broken in half.
Scanning electron
micrographs (SEM) revealed
fractured fastener surfaces
and separated grain
boundaries in the steel. The
screws had also lost ductility.
The Culprit: HASCC!

23. Hydrogen & Embrittlement
HASCC starts with hydrogen.
Hydrogen embrittlement is associated
with galvanic action. However, steel
fasteners are not necessarily weakened
by galvanic corrosion itself. Rather,
hydrogen generated by galvanic
action attacks the steel.
Even if steel is protected from galvanic
corrosion, hydrogen can attack it rapidly.
Screws attacked by Specialized fasteners have been
hydrogen lose ductility developed to avoid this risk.
and become embrittled
They typically show no
visible corrosion.

24. Source of Hydrogen
Galvanic action creates electrical current.
Water in electrolyte separates into oxygen
and hydrogen.
Oxygen bonds with the anode and
oxidizes the metal. Since oxides have little
structural strength, the anode weakens
and corrodes.
Hydrogen is attracted to the cathode and
penetrates into the metal.
This process is similar to the laboratory procedure for
separating water into hydrogen and oxygen by
passing electrical current through it, a process called
electrolysis.

25. Hydrogen Diffuses into Steel
Hydrogen, the smallest atoms, can
penetrate “solid” steel.
Atoms lodge in voids in steel’s crystal
structure.
Single hydrogen atoms are unstable
and bond with other hydrogen atoms.
The larger H2 molecules put pressure
on the surrounding steel molecules.
This creates internal tension in steel, This scanning electron
enlarging its grain boundaries and
microscope (SEM) image of
reducing ductility.
steel shows enlarged grain
As this process continues, the steel boundaries indicative of
can no longer maintain its structure hydrogen embrittlement.
or bear its design load, and can fail.

26. The Role of Case Hardening
Hydrogen has little effect on
Case “mild” (soft) steel.
Rockwell Many architectural fasteners,
Hardness however, are case hardened,
HRC 52 min.
In case hardening, low-carbon
steel is heated in high-carbon
environment to infuse extra
carbon into metal’s surface.
This hardens steel’s outer layer
Core (“case”) and makes it brittle.
Rockwell
Hardness Case hardening makes self-
HRC 32-40 drilling screws hard enough
to drill and tap into structural
steel or tap concrete.
HASCC affects steel of Rockwell hardness ≥ HRC 35. The harder the steel,
the more susceptible is it to HASCC. Case-hardened fasteners are typically
HRC 52 on the case and HRC 32 to 40 in the core.

27. Hydrogen Embrittlement & Stress
In case-hardened fasteners, the very hard/brittle outer layer is most
vulnerable to HASCC. Weakening the outer layer transfers the load onto
the core of the fastener, a significantly small diameter of steel than the
original design. The design load can overwhelm this reduced fastener
diameter, leading to failure.
This cross-section of a failed case-
hardened fastener shows the hardened
outer case, which was embrittled by
hydrogen, and the inner ductile core,
which failed under the design load.
B.Application Induced Hydrogen Assisted
Stress Corrosion Embrittlement Mode
C.Ductile and Embrittlement Mode/
Strength loss
D.Complete ductile failure due to reduced
cross-sectional area of fastener/ unable to
sustain load of application

28. Stress Concentration
Stress increases steel’s susceptibility to embrittlement.
Stress concentration occurs at screw heads for 3
reasons:
1. MANUFACTURING:
Deformations required
to form steel rod into
screw heads induces
stress into metal.

29. Stress Concentration
2. CLAMPING FORCES
When screws are tightened, their
heads bear on the surface of the
object being attached.
This places the area of the shank
immediately under the head into
tension, inducing stress.

30. Stress Concentration
3. OUT OF ALIGNMENT
Screws are rarely perfectly
perpendicular to surfaces
they are attaching.
When tightened, uneven
pressure is put on head by
oblique angle at which it is
installed. A test for resistance to hydrogen
embrittlement closely mimics this real-world
This puts additional stress on situation. The fastener is screwed through
two plates of dissimilar metals. A shim is
one side of fastener at placed under one edge of the top plate,
juncture of head and shank. creating an angle between the two plates and
placing the screw at an oblique angle with
respect to one of them.

31. Stress Cracking
Galvanically generated
hydrogen at stress points
leads to microscopic
cracking.
Micro-cracks further
concentrates stress points.
Once propagated, cracks
can spread quickly through
hardened steel.
Metallurgists call this
cracking “Hydrogen Assisted
Stress Corrosion Cracking”
(HASCC).

32. Plating and Hydrogen Embrittlement
Case hardened fasteners must still be protected against rust
and galvanic corrosion.
Standard plating of case hardened fasteners generates
hydrogen that could contribute to “Hydrogen Embrittlement”.
This is unlikely, because platers bake hydrogen out of
fasteners @ 400+ for several hours after treatment.
But you cannot bake-out Hydrogen from continuous Galvanic
reactions on the job.
In low stress, completely dry areas, zinc or other plated, case
hardened fasteners, may work well, or, if exposed to moisture
it can pose a risk for delayed failures.
Case hardened fasteners can be protected with high-
performance anti-corrosion coating. But it does not stop
hydrogen diffusion into hardened steel.
However, new innovations – described in next section – will.

33. HASCC Recap
Galvanic action between dissimilar metals generates
hydrogen.
Hydrogen penetrates hardened steel and creates internal
stresses that weaken fasteners.
This process occurs primarily in high hardness/case
hardened parts.
Stress concentrations initiate micro-cracking that can
propagate across fastener.
HASCC can occur days, months or years after fastener
installation if connection is exposed to moisture.
Failure is often sudden and without warning. No rust is
seen.

34. Benefits of Self Drilling Screws
Self-drilling screws require just seconds of
installation time and labor VS that required for
nuts-and-bolts, rivets, and other fasteners requiring
pre-drilled holes.
Fasteners install in single, fast operation using a
power driver.
They are much faster than two-handed bolt-and-nut
Dril-Flex.exe
installations, and more practical where the back
side is not accessible for installing a nut.
With hundreds of thousands of fasteners used in
large buildings, this represents an enormous
savings in labor.
Use to install windows, cladding, curtain wall,
framing, anchors, equipment, fixtures, and other
building components.

35. The Remedy for HASCC
Self-drilling fasteners have to be case hardened in
order to drill and tap substrates – but case
hardening makes them vulnerable to failure.
Fortunately, there is a solution to fastener HASCC
hazards.

36. Design of Self Drilling Screws
Select head style for
easy installation,
Attaching Into Metal: acceptable profile,
Lead threads tap threads and pull-over
resistance
into substrate, so
Select
substrate acts as nut. thread style
to hold in
They are available in substrate
many specialized
configurations to suit a Lead threads cut
wide range of threads into (tap)
substrate for pull-out
construction applications. resistance
Tip drills hole and
removes shavings

37. HASCC-Resistant Fasteners
Vir
tua
to lly Im
HA m
SC un
C e

38. A Metallurgical Marvel
There are two ways to achieve this performance:
2. Selectively Hardened Fasteners
3. Bi-Metal Fasteners
Hardened for Ductile for structural
drilling and performance and
tapping HASCC-resistance.

39. Selectively Hardened Fasteners
Certain hardened fasteners are
made from special, high-carbon
steel. Since the alloy already
contains the carbon needed to
DUCTILE WHERE harden the steel, fasteners do not
NEEDED have to be placed in a high-carbon
Grade 5 heat treat environment during heat treatment.
in load-bearing
area of fastener This also makes it possible to
selectively harden the fastener
drill and tapping tip.
HARDENED WHERE Tip of screw is passed through an
NEEDED electrical induction coil that heats
Selectively hardened and hardens drill-point and lead-
point and tapping
threads without affecting rest of
threads HRC 52
shank.

40. 2. Bi-Metal Fasteners
Use where stainless steel is required for
increased resistance to corrosive
environments.
300 Series Stainless steel is not
hardenable by heat treatment. Stainless
steel is not suitable for selective hardening. 300 Series
Stainless
Instead, a high-carbon steel tip is fused Steel Head
onto stainless shank. and
High carbon tip is then selectively Shank
hardened using induction-coil heating.
High-Carbon
Steel Tip,
Selectively
Hardened
Recommended
for exposed
fasteners.

41. Corrosion-Resistant Coatings
Even stainless steel attachments are not immune to galvanic
corrosion and the elements.
Metallic, polymer-based, anti-corrosion coatings are recommended
on both selectively hardened and bi-metal fasteners to provide
galvanic protection and to lubricate the threads for dissimilar metal
connections.
Coating can be color matched as required.
Bi-Metal Fastener: Before coating, above. After coating, below.

42. PROOF
Steel and aluminum plates are connected by fasteners and
sprayed with a 5% salt-water solution, an electrolyte.
Conventional fasteners fail due to stress concentration at screw
heads that accelerates embrittlement. HASCC
Neither selectively-hardened nor bi-metal fasteners fail.
HASCC-
resistant
fasteners
are not
affected
Standard
case-hardened
fasteners failed

43. PROOF

44. PROOF
HASCC-resistant
fasteners, securing
facade have been
exposed to marine
and urban
atmosphere and
earthquakes during
two decades of
service.
US Bank Building/
Los Angeles, CA
Pei Cobb Freed Partners

45. Best Industry Practices
In applications where dissimilar
metals will be in contact, specify
selectively-hardened self-drilling
fasteners to resist HASCC.
In aggressive environments requiring
stainless steel for protection against
visible corrosion, specify bi-metal self-
drilling fasteners with a selectively-
hardened tip to resist HASCC.

46. FASTENERS FOR
EXTREME LOADS
Fasteners exposed to extreme loads
also require special attention to HASCC.

47. Extreme Loads
During extreme loading, structures are briefly subjected to
loads far higher than normal operating loads.
Risks can include:
• Hurricane & Tornado, including windblown missile impact
• Earthquake
• Accident, including industrial accident, vehicular collision,
etc.
• Redistribution of load due to failure of other building
elements
• Explosion, including boiler, natural gas leaks, attack
If there is reason to suspect a risk, it should be designed in.
Determination Estimate Risk-Resistant
of Risk of Risk Loads Design

48. Hurricane and Tornado Loads
Use building codes and regional history to predict loads.
High-speed winds create
extreme atmospheric
pressure differentials
between the interior and
exterior of building
enclosures.
High-velocity, windblown
missiles create extreme
impact loads.

49. Blast (Explosion) Loads
Blast resistance should be designed into
structures:
Containing volatile materials
With high-security profile
With strategic importance to an
organization or mission
That are or have occupants considered The attack on Oklahoma City
targets for attack Federal Building provoked rethinking
Located near possible targets of need for blast-resistance.
That are “Essential Facility” that must
remain functional after disasters due to
importance to public health and safety: Blasts also occur due to gas
• Hospitals leaks, boiler malfunction,
• Fire/rescue/police stations
• Toxic-material storage
and accidents.
• Air traffic control
• Critical defense installations.

50. Extreme Loading-Building
Envelope
Hurricane, tornado and
exterior blast loads are
applied first to building
cladding and fenestration.
These elements either
absorb the load – by
deformation or failure – or
transfer load to other
structural elements.

51. Seismic Loading
Violent, cyclical
accelerations place
extreme loading on
all building
components, not
just structural
members.
Failures of non-
structural elements
can injure or kill
people and make
buildings unusable.

52. Extreme Loading of Fasteners
Under extreme loading, if a structural
element does not fail, and it does not
deform sufficiently to absorb all the
load energy – that is, if it is designed to
withstand the load – then the load is
transferred to the fasteners that hold it
in place and connect it to other
structural elements.
If the fasteners are ductile in nature,
they will deform, absorbing some or all
of the blast or impact energy, but may
still keep in place the element they are
attaching.
If fasteners are brittle, extreme
loading may cause them to fail.

53. Case-Hardened & Extreme Loads
The outer layer of case-hardened
fasteners is brittle and less ductile.
Under extreme loads, the brittle Hardened
outer case fails first, leaving the (brittle)
inner core to bear load. case
Core diameter <
Even though the core may be fastener diameter
ductile, its smaller area can
becomes overloaded and fail. Soft
(ductile)
Fasteners with incipient HASCC core
are even more likely to fail during
extreme loading. Cross-section of case-hardened fastener
Using ductile, HASCC-resistant fasteners helps assure full
design strength of fasteners can be used to resist extreme loads.

54. Where to Specify
Blast-resistant windows
Curtain wall framing
Building equipment
Critical life safety and
communications
equipment
Continuous service of
building enclosure
systems

55. OTHER TYPES
OF FASTENERS
HASCC-resistant fasteners can be
used to simplify a wide range of
special construction applications.

56. Concrete and Masonry Screws
Choice of
head styles Specifying concrete
and masonry Choice of
head
anchors also styles
requires
Grade 5
hardness for
consideration of
strength and
ductility
dissimilar metals
and corrosion
resistance. Hi-lo
thread
A variety of special taps into
masonry
Higher designs are
hardness for
tapping available to satisfy
threads
most construction
requirements.
Concrete Masonry

57. Pressure-Relief Fasteners
In buildings with potential for
interior explosions, special panels
can be designed to blow off and
relieve pressure, a built in safety
valve.
Examples include places where
highly volatile liquids are in use, or
storage for extremely fine dry,
materials subject to dust-explosion.

58. Pressure-Relief Fasteners
panel
Pressure-relief panels are not separates
actually held in place by fastener panel from framing
member
heads. Panels have an centering
device
attachment-hole larger than the
fastener-head, and a special framing
aluminum washer retains the
panel in position.
aluminum
washer
Under explosive pressure, pressure-
collapses
relieving
washers fail and allow panels to washer
blow off, venting the pressure. Normal Explosion
The panel is tethered to keep it
from becoming a dangerous
missile.
HASCC-resistant 300 series
stainless steel fasteners are
used in assembly.

59. Pressure-Relief Venting

60. Threaded Rod Anchors
1/4-20 & 3/8-16
Threaded rods are used to support fire-sprinklers and other essential building
services. These fasteners simplify installation while protecting against potential
failures of other fastening methods that are not positively engaged in the
structural materials.

61. Sealing Washers
Integral head a washer-
face designs along with
high performance washer
material help prevent leaks
through building envelope.

62. SUMMARY
Manage Your Risk
Fasteners are critical components
of buildings.
A/Es must be aware of their
professional responsibility to
specify fasteners that fulfill design
intent and provide safe and
durable connections.

63. HASCC-Resistance
HASCC can cause sudden, catastrophic
failures when self-drilling or self-tapping
screws are used in conditions with dissimilar
metals and the potential for exposure to
moisture.
It is not safe to assume that contractors will
be aware of these issues and will select
anything other than standard fasteners.
Specify accordingly.
Selectively hardened and bi-metal self-drilling
fasteners mitigate risk because their load-
bearing sections remain ductile and virtually
immune to HASCC.

64. Economy
The lowest cost fastener may not be the
most economical when labor and service life
are considered.
Specialty fasteners can often save money
by providing lower installed cost.
Fasteners are typically less than .0025%
per dollar of project cost, but specifying
inadequate fasteners can cause up to 100%
of construction defect costs.

65. Sustainability
Most metal fasteners have recycled-
material content and are recyclable.
New corrosion-resistant finishes
eliminate toxic heavy metals plating.
Durability over life of structure is the
most important measure of sustainability.

66. Thank you!
This concludes the American Institute of Architects
Continuing Education Systems Program.
Any Questions?
Gregg Melvin, Elco Construction Products
(815) 979-3249 - gmelvin@acument.com