Ask Joe Powder Nov-Dec 2017
Posted on Monday, November 27, 2017
I work for an overhead doors company
and we powder coat the extruded
aluminum rails for our full-view doors.
We have had issues in the past when that
department tried to change the window
caulking to something with silicone in it,
and now our management team is wanting
to change caulking again. I’m needing
your professional opinion and some
documentation to confirm that what we
experienced before is indeed true
Terry, Arthur, Ill.
Thank you for your question. You are
wise to be cautious before making the switch
to a silicone-based caulk. I read the article
that you forwarded and it is a very good
treatise on how adhesive failure can occur
with silicone contamination. In this case,
the adhesion involves adhesives and sealants
and not a powder coating. You also mention
that the operation had issues in the past with
the use of silicone window caulk. Hmmm,
you weren’t specific so I wonder what issues
were encountered. I can assume (and we
all know what can happen when we make
assumptions) and conjecture that the powder
coating exhibited film defects such as craters
and possibly “fish-eyes.” These occur when a
contaminant has a surface energy significantly
lower than the resinous portion of a powder
coating. Silicones and other oils, lubricants and
greases all fall under that category. Indeed, other
sources can include body lotions, cosmetics,
textile finishes and even some fragrances.
The contaminant can emanate as a mist, a
particulate or even on a molecular level as a
fume. One thing is for sure—most, if not all,
silicone-based materials will cause cratering
in a powder coating finish. Cleaning to avoid
contamination usually falls short of eliminating
the incidence of defects. And as the article
points out, most cleaning materials and methods
do not successfully remove 100 percent of a
silicone contaminant. Hence, run fast, as fast as
you can, from introducing silicone caulk into
your plant. You’ll be glad that you did.
Readers can access the article referenced in
this question with this link:
Please let me know if you have any further
– Joe Powder
Joe Powder is our technical editor, Kevin Biller. Please send
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