WINTER 2016

176 THE DISTRIBUTOR’S LINK
CARMEN VERTULLO TO BAKE OR NOT TO BAKE? from page 172
ASTM B850 is the most commonly referred to
specification for baking times of electroplated parts. It
does present information for baking of some parts that
should not normally be susceptible to HE and has
classifications for baking based on tensile strength that
overlap. Additionally, it states that steels of actual
tensile strengths of less than 1000 MPa (HRC 31) do not
require baking. Conventional wisdom would say this is
much too low for this recommendation and leads to
unnecessary baking.
How Do I Know If The Baking Was
Effective Or Not?
Post plating testing is a critical quality assurance
step for HE susceptible fasteners that are exposed to
hydrogen which cannot escape from the material on its
own. This is the only effective way to know if a lot of
fasteners have HE. Fortunately, HE testing as it relates
to the fastener supplier and user is relatively simple.
HE Testing Falls Into Three Broad Categories
[1] Product testing to ensure that a given lot
of fasteners is free from HE. This is the most
common and simplest type of testing and all suppliers of
HE susceptible products should be familiar with it.
Specifications which cover this kind of testing are ASTM
F606/F606M, ISO 15330, and NASM 1312-5. This test
can be done by a qualified test lab, but it is certainly
within the capability of any fastener supplier, user or
plating shop that recognizes a need to know the
effectiveness of their post-process baking strategy. It
involves putting the fasteners under a controlled load in
a test plate, waiting for some period of time (24 – 48
hours) and seeing if they fail or develop cracks. Not all
fasteners lend themselves well to specification testing
and occasionally the supplier and the user will need to
agree on a test method.
[2] Testing to determine if a fastener failure is
attributable to HE. This can be as simple as the
product testing mentioned above, or it could involve
complex and expensive laboratory failure analysis work.
Laboratory failure analysis results can be controversial
and it is very important that the requesting party know
exactly what they are asking for when they send the
samples in for test. Sometimes only the broken fastener
is available and not much can be determined for certain
but an opinion is rendered that may or may not be
accurate. Often the supplier is confronted with an enduser’s
lab report after the fact. This is one reason why it
is very important for the supplier to act promptly and be
well informed when confronted with a potential HE failure
report.
[3] Testing to determine if a particular
material, condition, process or combination
thereof would create or prevent HE. This kind of
testing is called HE susceptibility testing and involves
test coupons called notch bars, and an elaborate test rig
called a Rising Step Load Tester. This type of testing
would be used to qualify a particular coating or material,
and once passed would preclude the need for baking or
post-process testing, or to determine the minimum
required baking time for a process. It is also used to
monitor a process to ensure it stays in control.
Specifications ASTM F1940 and ASTM F519 are
examples of this kind of testing. HE Susceptibility testing
should be conducted only by qualified laboratories.
Even after reading this long article you probably have
more questions about HE relief baking and HE in general,
and there certainly is a lot more to know about HE. For
example, you may be wondering:
• Who is responsible for the fastener if the
baking is not effective?
• Can fasteners that have not been baked be
baked later on?
• Can fasteners that have hydrogen
embrittlement be baked again to relieve the
embrittlement?
• How can I know for sure that my plated
fastener have been properly baked?
• Specs say that even if I do everything right HE
might still occur –what’s the deal?
• What should fastener suppliers do to properly
make decisions regarding baking and to
manage the risks associated with
electroplating fasteners?
• What should we know about environmental
hydrogen embrittlement?
Our next article will answer these questions and go
into detail on the kinds of HE testing that suppliers and
end-users can conduct, HE failure investigation, and the
do’s and don’ts of using test labs for HE testing.
CONTINUED ON PAGE 178