Lin, C. T. (Chhui-Tsu)
M.S. (Master of Science)
Department of Chemistry and Biochemistry
Phosphate coating||Steel||Metal coating||Chemical tests and reagents
The up-to-date industrial pretreatment for metals can be categorized as a multistep coating process. This process is designed to protect the metal against corrosion by exposing the metal to a phosphating bath. The result is the formation of an insulating layer of metal phosphates. This normally precedes the application of an organic coating. The phosphate conversion is a successful state-of-the-art technique, yet it has certain disadvantages. Disadvantages include human exposure to toxic compounds, excessive waste generation, energy consumption, and labor. Recently, a novel metal surface pretreatment technique, in-situ phosphatizing coating (ISPC), has been developed in our laboratory. The main goal of ISPC is to form a metal phosphate layer on the metal in-situ while an organic coating is applied. Dispersing an in-situ phosphatizing reagent (ISPR) into the paint formulation forms the ISPC. The formation of a metal phosphate layer is verified through FT-IR and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The performance of the dry paint film is evaluated using several analytical techniques. The corrosion resistance of the organic coating is studied with electrochemical impedance spectroscopy. Adhesion properties are measured with cathodic delamination and American Society for Testing and Materials (ASTM) tests. The viscosity o f the wet paint is determined with a Brookfield digital rheometer. The t selection of an efficient phosphatizing reagent is a challenging task that needs to be performed. Our research focused on selecting three compounds to be studied as potential phosphatizing reagents. The ISPRs are nitrilotris(methylene)-triphosphonic acid, phenylphosphonic acid, and 4-phosphono benzoic acid. The coating formulation (referred to as the control paint) adopted in this study is a volatile organic compounds (VOC)-free thermoset acrylic latex system from the Sherwin-Williams Company. Results on the performance properties of these potential ISPC formulations were obtained. Based on the data obtained, the ISPC that was superior compared to the control in terms of protecting the metal against corrosion was the one in which phenylphosphonic acid was used.
Muñoz, Carmen L., "The effect of phosphatizing reagents in the coating performance of an in-situ phosphatizing coating applied on cold-rolled steel" (1999). Graduate Research Theses & Dissertations. 5540.
xii, 177 pages
Northern Illinois University
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