WINTER 2021
Distributor's Link Magazine Fall 2020 / Vol 44 No 1
Distributor's Link Magazine Fall 2020 / Vol 44 No 1
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98<br />
THE DISTRIBUTOR’S LINK<br />
ROB LaPOINTE FASTENER SCIENCE: AVOIDING CATASTROPHIC FAILURE IN PLATED SOCKET-HEAD CAP SCREWS from page 8<br />
If, however, corrosion resistance is also needed, the<br />
SHCS is often electro-plated with zinc as a secondary<br />
process after manufacturing to provide this feature.<br />
Electroplating can lead to problems with the durability<br />
of the fastener. High-strength fasteners that have been<br />
electroplated can suffer catastrophic failure soon after<br />
loading them in an installation due to a phenomenon<br />
known as hydrogen embrittlement.<br />
Hydrogen embrittlement is a condition where the<br />
presence of hydrogen in the fastener can cause a<br />
sudden brittle fracture to occur after the fastener is<br />
loaded. The fastener is exposed to hydrogen during the<br />
plating process and if the hydrogen is not removed, it<br />
can cause catastrophic failure. The risk of failure is real<br />
and requires strict and specific mitigation procedures to<br />
be followed if it is to be free of the potential of hydrogen<br />
embrittlement. The user of an electroplated high-strength<br />
SHCS, is responsible to ensure that all the correct<br />
safeguards against hydrogen embrittlement have been<br />
followed and the fasteners have been properly tested for<br />
the presence of hydrogen. It may be surprising, but there<br />
are suppliers of these high-strength plated fasteners<br />
who do not follow standardized protocol to ensure that<br />
plated products are free of hydrogen embrittlement.<br />
You should never assume that if a supplier is making<br />
these fasteners available, then they are following all the<br />
rules to safeguard the product. If a high-strength plated<br />
product is required for the application, it is advisable<br />
to purchase these fasteners from a company who<br />
specializes in plating socket-head cap screws. Quality<br />
distributors of plated socket-head cap screws, such<br />
as Solution Industries (www.solutionind.com) know the<br />
risks involved and take all the necessary precautions by<br />
strictly following proper protocol.<br />
Proper protocol begins with the engineering<br />
specification such as ASTM A574. A574 specifically<br />
states that when applying a protective or decorative<br />
coating, precautions should be followed such as those<br />
found in the specifications ASTM F1940 and ASTM F606.<br />
These include testing procedures to verify fasteners to<br />
be free of the embrittling effects of hydrogen. Plating<br />
specifications such as ASTM B633 and ASTM F1941<br />
require mitigation procedures for plating high-strength<br />
fasteners to remove the hydrogen absorbed by the<br />
fastener during the plating process. Although these<br />
procedures are mandatory, they are not always followed.<br />
The user must verify that they are followed by examining<br />
the plating certificate and comparing it to the standard.<br />
Also, be advised that hydrogen embrittlement relief<br />
procedures set by standards such as ASTM F1941<br />
(Figure 3) are a minimum and that minimum may not be<br />
suitable for every product or situation. These minimums<br />
can be improved upon, if necessary, by contract with the<br />
plating company.<br />
FIGURE 3 TABLE 4 FROM ASTM F1941 LISTING MINIMUM HYDROGEN EMBRITTLEMENT RELIEF TIMES,<br />
STRESS DURABILITY TESTING METHODS AND PROCESS CONTROL SPECIFICATIONS.<br />
CONTINUED ON PAGE 156
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