MAY, Mousa, WANG, Heming and AKID, Robert (2013). Bond strength of hybrid sol–gel coatings with different additives. Journal of Coatings Technology and Research, 10 (3), 407-413.
Abstract
The hybrid sol–gel coating on Al 2024-T3
was modified by adding polyaniline, TiO2, or c-Al2O3
nanoparticles in the formulation separately. The coating
was then used as an adhesive to bond Al 2024-T3
alloys, forming a single lap joint. The bond strength of
the sol–gel coating was investigated using a universal
tensile test machine. The lap shear strength of the
original sol–gel coating was about 1.38 MPa and it was
increased up to 2.26 MPa after the modification by
adding 0.05 wt% PANI microparticles in the sol–gel
coating. The small increase in strength was attributed
to an improvement in its adhesive flexibility because of
incorporation of the long-chain organic polymer in its
structure. Furthermore, the addition of different
amounts of TiO2 nanoparticles in the unmodified sol–
gel coating also led to an increase in shear strength
compared to the undoped sol–gel coating. Typically, a
sol–gel coating containing 2.0 wt% of TiO2 recorded
the highest adhesive strength of about 4.0 MPa. A
similar increase in strength was observed when doping
c-Al2O3 nanoparticles into the original hybrid sol–gel
coating. Adding 0.5 wt% of c-Al2O3 in the sol–gel
coating increased the adhesive bonding strength up to
4.48 MPa. The fracture surface of the specimen was
separately observed by SEM and Optical Microscopy
in order to examine potential evidences of mechanism
and nature of failure. The reason why the adhesive
strength increased after the modification of the sol–gel
coating is discussed in this article.
Keywords Hybrid sol–gel, Coating, Bond strength,
Nanoparticle
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