Blister Test for Measurements of Adhesion and Adhesion Degradation of Organic Polymers on ...

247 Pages·2013·4.09 MB·English

by  Brendy Rincon T

BLISTER TEST FOR MEASUREMENTS OF ADHESION AND ADHESION DEGRADATION OF
ORGANIC POLYMERS ON AA2024-T3

Dissertation

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University

By
Brendy Carolina Rincon Troconis, M.S.
Graduate Program in Materials Science and Engineering

The Ohio State University
2013

Dissertation Committee:
Professor Gerald S. Frankel, Advisor
Professor Rudolph G. Buchheit
Professor Heather Powell
Copyright by
Brendy Carolina Rincon Troconis
2013
ABSTRACT

Coatings are designed to provide protection to the underlying metal, but a key
parameter for coating performance is adhesion. The coating can act as a barrier and also
as a source of inhibitors to mitigate corrosion. However, even if a coating system
contains the most efficient corrosion inhibitor species, no protection is imparted if the
primer is not well adhered to the substrate. Surface preparation prior to coating
application is critically important for controlling adhesion. However, there is a lack of
understanding of what controls adhesion. Numerous techniques have been developed in
the last decades to measure the adhesion strength of coatings to metals. Nonetheless,
these techniques are characterized by at least one of the following disadvantages: they
are non-quantitative, non-reproducible, performed in dry conditions, or overestimate
adhesion as a result of energy consumption by other phenomena, such as plastic
deformation.
In this study, the Blister Test (BT) is used to measure adhesion strength and
adhesion degradation. The principal advantage of this technique is that it provides a
measure of the normalized energy needed to initiate/propagate a crack at the
substrate/polymer interface. This is a quantitative measurement that is not given by any
other technique. Also, the BT can be performed in presence or absence of a wetting
liquid, there is no system contamination via substance diffusion from an adhesive placed
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on top, and it offers the ability to study the effects of a range of parameters. Furthermore,
the amount of plastic deformation during the test is minimized because the peeling angle
is kept lower than 90°. In addition, the BT simulates the actual stress situation in the
coating/substrate interface. Finally, but not least important, it has been shown to be
reproducible.
The effects of roughness and surface topography were studied by the BT and
Optical Profilometry, using AA2024-T3 substrates, with either random or aligned
abrasion that were coated with polyvinyl butyral (PVB). The random abrasion generated
a surface with lower average roughness due to the continual cross abrasion of the
grooves. Adhesion strength results from the BT were reproducible and helped to discern
effect of different mechanical treatments. Roughness degree and surface topography were
found to be very important factors for adhesion strength. Randomly abraded samples
were found to have higher adhesion strength than aligned abraded samples. Microscopic
peeling angle was found to be important for the determination of adhesion strength. An
adhesion strength indicator was defined and found to be effective in sensing adhesion
strength.
The effectiveness of standard adhesion techniques such as ASTM D4541 (Pull-off
Test) and ASTM D3359 (Tape Test) was compared to the BT. Also, different attempts to
measure adhesion and adhesion degradation of organic polymers to AA2024-T3 were
tested. The pull-off test does not produce adhesive failure across the entire interface for
single- or double-primed samples even after a forced curing procedure. Therefore, pull-
off test results do not represent true adhesion strength. The tape test is a very qualitative
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technique and does not discern between the effects of different coating systems on the
adhesion performance. The BT is a very versatile technique that allows calculation of
adhesion strength. It produces adhesive failure of the primer studied, is very reproducible,
and is able to rank different coating systems. It was found that pretreatment incorporation
into coating processes improves adhesion strength of pigmented epoxy to
cleaned/desmutted (C/D) substrate: No conversion coating (no CC) < Trivalent
Chromium Process (TCP) ≈ Non Chromium Process (NCP) < Chromate Conversion
Coating (CCC). In contrast, for non-C/D samples, CCC < NCP ≈ TCP.
The effects of C/D step and CC on the adhesion strength of acetoacetate to
AA2024-T3 and the effects of improper water rinse temperature after cleaner were also
assessed using the BT. The results showed that pretreatments improve the adhesion
strength of acetoacetate primer on AA2024-T3, but the comparative behavior of the
different CC tested depends on the specific treatment. The equation used for adhesion
strength calculations needs to be adjusted and improved in terms of the effect of coating
thickness on adhesion strength. Process control is of paramount importance for the
performance of acetoacetate coated systems applied on AA2024-T3. The lack of thermal
activity in the water rinse after cleaning step produces deleterious effects on the adhesion
and blistering resistance of CC systems and contamination of baths as a result of
contaminant transfer in the process line by the sample being treated.
Finally, a test sample incorporating a coated and scribed Al alloy panel and
uncoated through-hole fasteners (Ti, SS316, AA2024-T3) was designed to provide
accelerated response during atmospheric corrosion testing in the field (long-term beach
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exposure) or in laboratory chambers (ASTM B117). The results after only three weeks of
exposure to ASTM B117 correlated well with long-term beach exposure, allowing rapid
ranking of different coating systems. Of the fastener materials studied, visual observation
indicated that the worst attack occurred near SS316 fasteners even though Ti-6Al-4V
fasteners are more-noble. The volume of AA2024-T3 lost during exposure was also
largest for samples with SS316 fasteners. The difference between SS316 and Ti-6Al-4V
was explained by Scanning Kelvin Probe measurements and the available cathodic
current, which was measured in chloride solution.

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Dedicated to
My fiancée, Nasser G. Lopez, and
My parents, Nelson E. Rincón Gutierrez and Oladis M. Troconis de Rincón

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ACKNOWLEDGEMENTS

I would not have been able to reach this goal without the presence in my life of
several people who made of this journey a more viable, organized, guided, harmonic, and
pleasant event than it would have been without them.
This work was funded by the Strategic Environmental Research and Development
Program, Project WP 1620.
I want to thank my advisor, Dr. Gerald S. Frankel, for his invaluable guidance
during my Ph.D. in the professional, but also in the personal aspect. Working with you
has made me a better person, student, researcher, teacher, and speaker. I really appreciate
all your time, patience, accessibility, thoughtful advices, constructive criticism, and
encouragement, especially during the very difficult times. Thank you for giving me the
opportunity to be your student and also to be part of such a distinguished, diverse, and
very friendly research group as it is the Fontana Corrosion Center. I will treasure in my
heart all the wonderful moments I lived in this group. I also want to thank Dr. Rudy
Buchheit for all the encouragement, help, and great insight in my research and future
plans. Also I would like to thank Dr. Heather Powell for being part of my oral
examination committee and for advise me and guide me on my Ph.D. and future plans.
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To all the past and present members of the Fontana Corrosion Center who
supported, encouraged, and helped me, specially to Dr. Fariaty Wong, Dr. Bastian Maier,
Shuyan Qiu, Dr. Mariano Kappes, Dr. Belinda Hurley, Dr. Anusha Chilukuri, Dr.
Federico Gambina, Dr. Liu Cao, Meng Lopez-Garrity, Omar Lopez-Garrity, Severine
Cambier, Jiheon Jun, Shanshan Wang, Pitichon Klomjit, Jinwook Seong, Sean Morton, I-
Wen Huang, Zhicao Feng, Jermain Onye, David Cole, and the rest of the group. Ms.
Christine Putnam thank you very much for being always patient and efficient through the
administrative work you provide.
I want to express my gratitude to Dr. Hamish Fraser’s research group for allowing
me to use their Multiprep Systems to prepare my samples. Also, I want to thank Carol
Lee and Francisco Chaparro for their instruction and guidance on Tensile Test.
In addition, I want to thank several staff members from the Materials Science and
Engineering, Chemical and Biomolecular Engineering, Physics, and Chemistry and
Biochemistry Departments such as Steve Bright, Ross Baldwin, Ken Kushner, Peter
Gosser, Jerry Hoff, and Paul Green. For help in performing Dynamical Scanning
Calorimetry on samples, facilitating tools and equipment for different purposes, and for
their suggestions and guidance in designing the sample preparation and system setup for
the BT. Also, I want to express my gratitude to Dr. Lisa Hummel for her help in
performing X-ray Photoelectron Spectroscopy and guidance during data processing.
I want to extend my gratitude to Dr. Joe Osborne for his instruction, advice, and
guidance to perform the tape test. Also, I want to thank Prof. Nathalie Romero from
“Centro de Estudios de Corrosion Oladis Troconis de Rincon” in Venezuela, Kirk
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Kramer from Henkel Corporation, and Craig Matzdorf, Bill Nickerson, Frank Pepe,
Susanna Kaumeyer, and Brenna Skelley from NAVAIR for their collaboration and help
in sample preparation.
Marianna Aboulhosn and Carlos Torres thank you for your support and care,
allowing me to stay in your home during the stressful moments renewing my student visa
in Canada. My first dissertation chapters were written comfortably thanks to you.
I want to express my gratitude to the Family Lopez-Garrity for making me one of
your own and establishing a family environment away from home.
Thank you mami and papi, all my admiration goes to you. You have guided me
wisely with patience and love through the path of life, aiding me to shape my life. Thank
you for always supporting and encouraging me to achieve my dreams. Mom you are my
role model and inspiration. To my siblings, Szuly, Ricardo, and Nelson; and my chosen
siblings, Marlon, Ana, and Fabiola for always been there for me. To my nephews, nieces,
and god children for brightening my days and fill them with joy and happiness.
Nasser Lopez, my fiancée, thank you for all your love, support, patience, help,
and understanding throughout this process. Being next to you during these years gave me
strength and motivation to continue and never quit pursuing my dreams. Furthermore,
thank you for applying your very convenient engineering skills, developing filter
softwares for data processing of the Blister Test and Scanning Kelvin Probe data.
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