coating methods - CHAPTER 27 APPLICATION METHODS The...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
CHAPTER 27 APPLICATION METHODS The successful use of organic coatings depends to a great extent upon their correct application. The general requirement placed upon the various coating methods used is that they be capable of depositing a layer of the coating material approxi- mately a thousandths of an inch thick. This layer must then be distributed with maximum uniformity and complete continuity. The selection of an application method is determined by the type of coating material applied, the coating thickness and final properties required, the quantity of parts being coated, and the transfer efficiency of the application method. The transfer efficiency is the percentage of paint solids con- sumed that actually coats the merchandise. Trans- fer efficiencies vary from 30 to almost 100%; in other words, some application methods waste 7070 of the consumed paint, while others are nearly waste-free. The most widely used application methods are discussed subsequently; each has specific advan- tages and limitations. Being familiar with all these methods will assist the manufacturing engineer in selecting the proper method for a specific appli- cation. Although one process may be suitable for one installation, it may not be suitable for another. Table 27-1 summarizes the capabilities of the various application methods. SUBSTRATE PREPARATION The successful performance of a finish applied to any substrate is dependent upon the proper conditioning of the substrate surface. Failure to properly prepare the substrate can result in paint peeling, flaking, or blistering, underfilm rusting of ferrous metals, and underfilm corrosion of non- ferrous metals. 1 Although in theory each surface should be chemically and physically clean before painting, in practice the choice of an adequate surface preparation or pretreatment is often dic- tated by the economics of the particular situation. To gain full advantage of the coating character- istics, surface preparation should be part of the finishing process. in general, substrate preparation serves to(1) remove soils or imperfections from the substrate, (2) create a surface susceptible to bond- ing, and (3) establish a chemical coating on the surface that will slow corrosion in case the coating film is damaged. The soils to be removed may range from oil, grease, and wax-based soils to defects such as oxidation, rust, corrosion, heat scale, tarnish, and smut. Oils and greases are generally removed with alkaline or solvent-type cleaners, whereas natural conversion coatings are removed with acidic or chelated alkaline cleaners. For additional informa- tion on cleaning procedures and solvents, refer to Chapter 18, “Cleaning.” Mechanical cleaning methods are discussed in Chapter 16, “Mechanical and Abrasive Deburring and Finishing. With some cleaning techniques, a surface suit- able for bonding may be produced while removing soils or imperfections; with other techniques, it may be necessary to roughen the surface. A corrosion-inhibiting surface can be produced by phosphating, chromating, or anodizing.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern