Views: 0 Author: Site Editor Publish Time: 2023-02-16 Origin: Site
There are many destructive and non-destructive evaluation (NDE) methods for characterizing coatings.The most common destructive method is microscopic examination of mounted cross-sections of the coating and its substrate.The most common non-destructive techniques include ultrasonic thickness measurement,X-ray fluorescence (XRF), X-ray diffraction (XRD) and microhardness indentation.X-ray photoelectron spectroscopy (XPS) is also a classic characterization method for studying the chemical composition of nanometer-thick surface layers of materials.Scanning Electron Microscopy combined with Energy Dispersive X-ray Spectroscopy (SEM-EDX or SEM-EDS) allows the visualization of surface textures and probes their underlying chemical composition.Other characterization methods include transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning tunneling microscopy (STM),and Rutherford backscattering spectroscopy (RBS).Various chromatographic methods have also been used,as well as thermogravimetric analysis.
The formulation of the coating depends primarily on the desired function of the coating as well as the desired aesthetics such as color and gloss.The four main components are resin (or binder), solvent (possibly water) (or no solvent), pigment,and additives.Research is ongoing to completely remove heavy metals from paint formulations.
Coating processes can be classified as follows:
Vapor deposition:Chemical vapor deposition
Metal Organic Vapor Phase Epitaxy.
Electrostatic Spray Assisted Vapor Deposition (ESAVD).
Certain extensional forms.
Molecular Beam Epitaxy.
Physical vapor deposition.
Cathodic arc deposition.
Electron Beam Physical Vapor Deposition (EBPVD).
Ion Beam Assisted Deposition (IBAD).
Pulsed laser deposition.
Vacuum evaporation, evaporation (deposition).
Pulsed Electron Deposition (PED).
Chemical and electrochemical techniques
Autophoretic,the registered trade name for a proprietary series of auto-deposited coatings designed for use on ferrous substrates.
Chromate conversion coating.
Plasma electrolytic oxidation.
Ion beam mixing.
Pickling and oiling, a steel coating.
High Velocity Oxygen Fuel (HVOF).
Dynamic Metallization (KM).
Plasma transfer wire arc thermal spraying.
Common forms of powder coating
Roll-to-roll coating process
Common roll-to-roll coating processes include:
Air knife coating.
Anilox roll coater.
Doctor knife roller coating.
Hot melt coating-when the desired coating viscosity is achieved by temperature rather than by polymer solution,etc.This method usually implies slot die coating above room temperature but hot melt roll coating can also be used; hot melt metering rod coating,etc.
Coating of Meyer bars.
Forward roller coating.
Reverse roller coating.
Silk screen coater.
Slot Die Coating Slot die coating was originally developed in the 1950's.Slot die coating has low operating costs and is an easily scalable processing technique that can rapidly deposit thin and uniform films while minimizing material waste.The slot die coating technique is used to deposit various liquid chemicals onto various materials such as glass,metals and polymers).The complex internal geometry of traditional slot molds needs to be machined or can be done by 3-D printing.Extrusion coating usually high pressure, often high temperature,and the web moves much faster than the extruded polymer.Curtain Coating Low viscosity,slots are perpendicular to the top of the screen,with a gap between the slot die and the screen.Slide Coating - bead coating with an angled slide between the slot die and the beads.Commonly used in multilayer coatings in the photographic industry.Slot die bead coating typically the web is supported by a roll with a very small gap between the slot die and the web.Tension web slot die coating no backing for the web.
Physical coating process.
This category is empty.