SUMMER 2016

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THE DISTRIBUTOR’S LINK
CARMEN VERTULLO HYDROGEN EMBRITTLEMENT Q&A - HELP FOR MANAGING ‘HE’ RISK IN FASTENERS from page 26
This would be a good time to consider changing
the coating to a non-HE inducing coating. We know that
most specifications require baking to be done within a
short time after plating. Recent specification changes to
ASTM F1941 removed the requirement for baking within
4 hours of plating, as this requirement was found to not
be instrumental in driving out the hydrogen.
So, yes fasteners that were not baked, or not
properly baked can be baked later on. There are some
considerations to take into account though. If corrosion
resistance or torque-tension control is of importance,
baking probably will diminish or completely eliminate the
effectiveness of some supplemental coatings such as
chromate conversion coatings or torque modifiers. These
coatings are designed to be applied over freshly coated
surfaces and simply re-applying them may not work. In
any case, it is a good practice to conduct HE relief baking
as soon as practical after plating for the sake of process
control and the elimination of a variable.
Can Fasteners That Have Hydrogen
Embrittlement Be Baked Again To Relieve
The Embrittlement?
This question is similar to the previous question
except that we now have product that has HE and it
may or may not have been baked. The strategy is the
same, except there will be a need to be extra vigilant
and ensure a higher level of assurance that the HE relief
baking has been effective. Increased sample size for HE
testing, more than one test per lot, and if re-processing
the lot entirely is the chosen option; strip, bake and then
test to ensure you now have a non-HE lot to work with.
Again, his would be a good time to consider
changing the coating to a non-HE inducing coating, and
the best option may be to scrap the lot and replace it
with fresh product, but be certain to understand why the
HE occurred in the first place so the problem does not
recur.
How Can I Know For Sure That My Plated
Fasteners Have Been Properly Baked?
This is one of the most important questions for the
fastener supplier to answer, and it must be answered
with confidence. If the supplier is processing the parts
themselves, then it is imperative that they audit their
plating vendors and ensure they have proper baking
equipment, modern control systems, unquestionable
process control and records, and all personnel in the
process are properly trained.
Under this scenario it is relatively easy to ensure
proper processing because the supplier has control over
it. It gets more difficult when the supplier purchases HE
susceptible product that has been plated by their supplier
or importer outside of their control. Many suppliers
prefer to buy product already plated because they think
it insulates them from liability if an HE problem were
to occur. Unless the supplier knows how their source
manages HE risk and has a thorough understanding of
their strategy this is not true.
The supplier must have a process in place that
properly calls out the plating, baking and testing
requirements on all orders. This should include the
applicable specifications and the time and temperature
for the HE relief baking requirement. Be sure the receiving
process checks to see that all of the requirements were
met and that each lot of product is in conformance
with the product specifications before it is selected for
processing. Lot control is essential.
The key to knowing that your HE relief baking strategy
is effective is post-plating HE testing of the processed
product. There are several different types of tests and
the test specifications do not cover all possible testing
scenarios. Often times some creativity is needed to
conduct an effective HE test. The supplier must be able
to specify the required testing and preferably do that in
agreement with the end user.
Some plating and product specifications explicitly
require testing for certain plated products and this
is often overlooked by the supply chain. Providing a
certification to a plating or a product specification may
imply that the product was tested in accordance with that
specification when in fact it was not. It is imperative that
suppliers and platers know what they are certifying to.
Fastener suppliers who purchase already plated HE
susceptible product should ask the supplier or importer
about their HE prevention strategy and get the applicable
process certifications with, or prior to, purchasing the
product. Do not wait until there is a HE failure to track
down the plating, baking and HE testing certifications
and test reports.
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