3. Thin metal and dielectric coatings are used to construct mirrors,
antireflection coatings, light valves, laser optics, and lens coatings.
4. Hard coatings sucha st itaniumc arbide, nitride,a nd carbon
produce wear-resistantc oatings for cutting tools.
5. Thin film coatings can be used to provide high temperature
environmental corrosionresistance for aerospace andengine parts,
gas barrier layers, and lightweight battery components.
6. Titanium nitrideisdeposited on watchbands and jewelry as ahard
gold colored coating.
7.2.1.5 Diffusion Coating
This method requiresapreliminary step followed by thermal treatment and
diffusion of the coating metal into the substrate. Ac ommercial material
known as galvannealed steel is made by coating steel with zinc followed by
heat treatment and the formation of an iron–zinc intermetallic coating
by diffusion.
7.2.1.6 Flame Spraying
The coating metal is melted and kept in the moltencondition until it strikes
the substrate to be coated. Aluminum and zinc are applied in this manner.
Flamesprayedaluminumhas alower density than pure aluminumbecause
of voids in the coating.
7.2.1.7 Plasma Spraying
This method is similar to flame spraying exceptthat forms of heating other
than afl ame are used.
7.2.1.8 Hot Dipping
Zinccoatings areapplied to steel sheets by immersion of the steel in amolten
bath of zinc to form galvanized steel. Asmallamount of aluminumisadded
to the bath to establish agood bond at the zinc–steel interface. The thickness
of the zinc coating is controlled by rigid control of the galvanizing bath
temperature, the speed of passage through the bath, the temperature of the
steel sheetbefore it enters the bath, and the use of air jets that exert awiping
actionast he steel sheet exits the bath.
7.2.1.9 Vacuum andV apor Deposition
This method is used primarily for the formationo fm etallic coatings on
nonconductive substrates. Common deposited coatings usingt his method
include aluminum coatings on plastics and rhodium coatings on mirrors.
Corrosion of Linings and Coatings
420
CAT8247—CHAPTER 7—17/10/2006—15:02—TRGANESH—XMLM ODEL B–pp. 403–485
antireflection coatings, light valves, laser optics, and lens coatings.
4. Hard coatings sucha st itaniumc arbide, nitride,a nd carbon
produce wear-resistantc oatings for cutting tools.
5. Thin film coatings can be used to provide high temperature
environmental corrosionresistance for aerospace andengine parts,
gas barrier layers, and lightweight battery components.
6. Titanium nitrideisdeposited on watchbands and jewelry as ahard
gold colored coating.
7.2.1.5 Diffusion Coating
This method requiresapreliminary step followed by thermal treatment and
diffusion of the coating metal into the substrate. Ac ommercial material
known as galvannealed steel is made by coating steel with zinc followed by
heat treatment and the formation of an iron–zinc intermetallic coating
by diffusion.
7.2.1.6 Flame Spraying
The coating metal is melted and kept in the moltencondition until it strikes
the substrate to be coated. Aluminum and zinc are applied in this manner.
Flamesprayedaluminumhas alower density than pure aluminumbecause
of voids in the coating.
7.2.1.7 Plasma Spraying
This method is similar to flame spraying exceptthat forms of heating other
than afl ame are used.
7.2.1.8 Hot Dipping
Zinccoatings areapplied to steel sheets by immersion of the steel in amolten
bath of zinc to form galvanized steel. Asmallamount of aluminumisadded
to the bath to establish agood bond at the zinc–steel interface. The thickness
of the zinc coating is controlled by rigid control of the galvanizing bath
temperature, the speed of passage through the bath, the temperature of the
steel sheetbefore it enters the bath, and the use of air jets that exert awiping
actionast he steel sheet exits the bath.
7.2.1.9 Vacuum andV apor Deposition
This method is used primarily for the formationo fm etallic coatings on
nonconductive substrates. Common deposited coatings usingt his method
include aluminum coatings on plastics and rhodium coatings on mirrors.
Corrosion of Linings and Coatings
420
CAT8247—CHAPTER 7—17/10/2006—15:02—TRGANESH—XMLM ODEL B–pp. 403–485