Sensitive methods for studying the environmental performance of protective coatings

The safe working lifetime of a structure in a corrosive or other harsh environment is frequently not limited by the material itself but rather by the integrity of the coating material. Advanced surface coatings are usually crosslinked organic polymers such as epoxies and polyurethanes which must not shrink, crack or degrade when exposed to environmental extremes. While standard test methods for environmental durability of coatings have been devised, the tests are structured more towards determining the end of life rather than in anticipation of degradation. We have been developing prognostic tools to anticipate coating failure by using a fundamental understanding of their degradation behaviour which, depending on the polymer structure, is mediated through hydrolytic or oxidation processes. Fourier transform infrared spectroscopy (FTIR) is a widely-used laboratory technique for the analysis of polymer degradation and with the development of portable FTIR spectrometers, new opportunities have arisen to measure polymer degradation non-destructively in the field. For IR reflectance sampling, both diffuse (scattered) and specular (direct) reflections can occur. The complexity in these spectra has provided interesting opportunities to study surface chemical and physical changes during paint curing, service abrasion and weathering, but has often required the use of advanced statistical analysis methods such as chemometrics to discern these changes. Results from our studies using this and related techniques and the technical challenges that have arisen will be presented.

Development of amorphous carbon protective coatings on poly(vinyl)chloride

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Impact of Sn/F Pre-Treatments on the Durability of Protective Coatings against Dentine Erosion/Abrasion.

For preventing erosive wear in dentine, coating with adhesives has been suggested as an alternative to fluoridation. However, clinical studies have revealed limited efficacy. As there is first evidence that Sn(2+) increases bond strength of the adhesive Clearfil SE (Kuraray), the aim of the present study was to investigate whether pre-treatment with different Sn(2+)/F(-) solutions improves the durability of Clearfil SE coatings. Dentine samples (eight groups, n=16/group) were freed of smear layer (0.5% citric acid, 10 s), treated (15 s) either with no solution (control), aminefluoride (AmF, 500 ppm F(-), pH 4.5), SnCl2 (800/1600 ppm Sn(2+); pH 1.5), SnCl2/AmF (500 ppm F(-), 800 ppm Sn(2+), pH 1.5/3.0/4.5), or Elmex Erosion Protection Rinse (EP, 500 ppm F-, 800 ppm Sn(2+), pH 4.5; GABA International), then rinsed with water (15 s) and individually covered with Clearfil SE. Subsequently the specimens were subjected to an erosion/abrasion protocol consisting of 1320 cycles of immersion in 0.5% citric acid (5 °C/55 °C; 2 min) and automated brushing (15 s, 200 g, NaF-toothpaste, RDA 80). As the coatings proved stable up to 1320 cycles, 60 modified cycles (brushing time 30 min/cycle) were added. Wear was measured profilometrically. After SnCl2/AmF, pH 4.5 or EP pre-treatment all except one coating survived. In the other groups, almost all coatings were lost and there was no significant difference to the control group. Pre-treatment with a Sn(2+)/F(-) solution at pH 4.5 seems able to improve the durability of adhesive coatings, rendering these an attractive option in preventing erosive wear in dentine.

Paints and protective coatings /

"NAVFAC MO-110."

Paints and protective coatings

"NAVFAC MO-110."

1987 census of manufactures.

Mode of access: Internet.

1987 census of construction industries.

"CC87-I-11."

1992 census of construction industries.

Mode of access: Internet.

Finite element analysis of residual stresses in metallic coatings through a compound casting

Al and Mg alloys are widely used in industry as main lightweight alloys. They have excellent properties, such as low density, high ductility, and high specific strength, and so on. Generally speaking, Mg alloys are better than Al alloys. However the corrosion of Mg alloys is much more difficult to control compared Al alloys. Therefore to combine these two lightweight alloys, a composite-like structure is an ideal solution since Al alloys can be used as protective coatings for Mg alloys. Compound casting is a realistic technique to get this coating system. In the current study, we numerically study the compound casting using finite element method (FEM) to make these two alloys, a composite-like structure, satisfy requirements to resist corrosion required from industry, in which the aluminum layer is acting as a protective coating for the magnesium substrate. Several finite element models have been developed by using the birth and death element technique and we focus on compound casting-induced residual stresses in the compounded structure. The numerical results obtained from the proposed finite element models show the distribution profiles of thermal residual stresses. We found the major factors influencing the residual stresses are the temperature to pre-heating the Al substrate and the thickness of Mg deposits. © (2014) Trans Tech Publications, Switzerland.

Considerations associated with the testing of external pipeline coatings

Reliable testing methodologies for the assessment of protective coatings are critical for ensuring the integrity and durability of pipeline coatings (such as field joint coatings) and the mitigation of pipeline corrosion. Currently the failure of joint coatings is one of the major concerns in corrosion protection of pipelines, although they represent only approximately 5% of the coated area in a pipeline system. This paper presents an overview of major testing methodologies currently used in the pipeline industry for the selection, testing, and life prediction of coatings, in particular field joint coatings. Particular focus is on the discussion of difficulties and limitations in testing methods for assessing pipeline coating cracking, cathodic disbondment and loss of adhesion. It is shown that there are limitations in current methodologies in evaluating the coating flexibility - a key parameter for avoiding coatings cracking during hydrostatic testing, cyclic pressure operation and field bending. Methodologies for assessing the effect of holidays in coatings on the cathodic disbondment of pipeline coating under excessively negative cathodic protection (CP) voltages also require improvement. Furthermore, methods for understanding the effects of coating wet adhesion on pipeline coating, cracking and disbondment also need attention. Some preliminary results for addressing some of these issues are also presented in this paper.

Fabrication of Electronic Materials from Australian Essential Oils

This RIRDC publication reports the findings and recommendations of the RIRDC funded study, "Fabrication of Electronic Materials from Australian Essential Oils". This project was undertaken to facilitate an expansion of the Australian Essential Oils Industry through the development of novel applications in the Electronic and Bio-Materials Industries. The findings presented in this report will provide value broadly across the Australian Essential Oils Industry, and more particularly to the growers involved in the production of tea tree, lavender and other essential oils. Several essential oils, namely tea tree oil, sandalwood oil, eucalyptus oil, alpha-pinene, d-limonene, lavender oil (a separate PhD project) and five major components of tea tree oil were tested. With the exception of sandalwood oil, all oils investigated were successfully polymerised. Importantly, this project determined that it is possible to use an environmentally friendly, inexpensive process of polymerisation to fabricate materials from essential oils in a reproducible manner with properties required by the optics, electronics, protective coatings, and bio-material industries.

Coatings and surface treatments for protection against low-velocity erosion-corrosion in fluidized beds

Surface coatings and treatments have been used to reduce material loss of components in bubbling fluidized bed combustors (FBCs). The performance of protective coatings in FBC boilers and laboratory simulations is reviewed. Important coating properties to minimize wastage appear to be high hardness, low oxidation rate, low porosity, high adhesion and sufficient thickness to maintain protection for a long period. Economic considerations and criteria for choosing a suitable coating or treatment are discussed for the different types of bubbling FBC. © 1995.