WINTER 2016

66 THE DISTRIBUTOR’S LINK
Anthony Di Maio
Anthony E. Di Maio attended Wentworth Institute and Northeastern University. In 1962 he
started working with Blind Fasteners as Vice-President of Engineering & Manufacturing for
two blind rivet manufacturers. He has been Chairman of the Technical Committee of the
Industrial Fasteners Institute (IFI) and is still involved in the writing of IFI specifications. In
1991, he started ADM Engineering and is working with Fastener Manufacturers developing
new fasteners and special machinery. He can be reached at ADM Engineering, 6 Hermon Ave.,
Haverhill, MA 01832; phone and fax 978-521-0277; e-mail: tdimaio@verizon.net.
WHAT IS THE BEST FINISH FOR A BLIND RIVET?
There are many types of finishes that are applied
to blind rivets. Some finishes are determined by the
application the blind rivet is being used in. Many blind
rivets have a painted surface of the same color as the
application.
Years ago, cadmium was the finish used on both
components of the blind rivet the blind rivet body and
mandrel. Cadmium became a finish that was reduced
in use for many reasons and then zinc plating became
popular. Both the rivet body and mandrel were zinc
plated with a clear dichromate surface.
Zinc plated blind rivets were used for many years,
until a problem occurred between the pulling jaws of
the setting tool and the zinc plating of the mandrel.
When the pulling jaws of the setting tool grip the
mandrel to set the blind rivet, the pulling jaws griping
teeth would crack the zinc plating and flake the zinc
plating. These flakes of zinc plating would lodge
themselves in the griping teeth of the pulling jaws and
cause the pulling jaws not to penetrate the surface of
the mandrel thus causing the gripping jaws to slip on
the surface of the zinc plated mandrel. This will cause
a mal-function of the setting tool and the blind rivet
could be set in the work piece. For this reason blind
rivet mandrels were not zinc plated but instead were
phosphate coated. The mandrel was manufactured
from phosphate coated wire thus giving the mandrel
surface a phosphate coating. The phosphate coated
mandrel would prevent the mandrel from rusting and
CONTRIBUTOR ARTICLE
the phosphate coating on the mandrel would not cause
the pulling jaws of the setting tool to slip on the surface
of the mandrel.
Aluminum blind rivet bodies are anodized. This
anodizing process would coat the surface of the blind
rivet body and prevent oxidization. Also aluminum blind
rivets have the rivet body and mandrel coated with a
surface protection liquid that is applied when the
components are tumbled and washed.
Steel blind rivets bodies are also coated with black
oxide that protects the surface of the blind rivet body
and prevents rusting.
The finishes mentioned are all good finishes that
protects the blind rivet components. In many cases, it
is the blind rivet application and the customers or
users request that determine which finish will be used
for the customer.
Just to recap, the following finishes are used for
blind rivets.
• Paint
• Cadmium
• Zinc with clear dichromate.
• Zinc with yellow dichromate.
• Anodize
• Oxide
• Phosphate coated mandrels.
All are good finishes and the most popular for steel
blind rivets is zinc with clear dichromate blind rivet body
and a phosphate coated mandrel.
ANTHONY Di MAIO