The Type I multi-sprayed metallic-ceramic coating (from two or more spraying applications and curing) is intended to be used for the prevention of heat sealing, oxidation, salt water corrosion and for protection from corrosion due to other corrosive environments. The coating material may be applied to jet engine parts. There may be an unfavorable effect upon the fatigue strength of basis materials beginning about 1000°F (538°C) due to diffusion of the Type I coating into the basis metals. Types II and III coatings are intended for general oxidation and corrosion prevention of basis metals in marine, above ground and underground applications. The Type II coating may be used with any basis metal capable of withstanding the elevated fusion temperature (1450 to 1520°F). As with Type I coating, there may be an unfavorable effect upon the physical properties of the basis metals due to diffusion of the coating materials. The Type III coating should be used primarily on basis metals not capable of withstanding processing temperatures above 350°F (177°C), with metal parts that may be prone to distortion at temperatures above 350°F, or if parts are too large for a furnace capacity for Type II application. The Type III coating is compatible corrosion-wise with the Type II coating and may be used to protect weldments of parts, welded after having been previously coated with Type II material.
The Type I, class 1 coating is intended to provide oxidation corrosion protection of parts up to temperatures of 1600°F (871°C) and to marine atmosphere corrosion protection where coated parts are exposed to elevated operating temperatures for time periods as stated in Table II which would render the coating conductive. This class coating is also intended to be used where the nature of the basis material of the part limits curing and post treatment temperatures to 650°F (343°C).
The Type I, class 2 coating is intended to provide oxidation corrosion protection, galvanic corrosion protection and marine atmosphere corrosion protection of ferrous alloys, titanium and titanium alloys and other metallic substrates. The coating also has current carrying capacity for static charges. The post curing treatment at 950° to 1100°F (510 to 593°C) as recommended in Table II provides for the sacrificial corrosion protection at the lowest processing cost. This class coating, because of these coating characteristics, is recommended to be used for parts wherever possible.
The Type I, class 3 coating is also intended to provide oxidation corrosion protection, galvanic corrosion protection and marine atmosphere corrosion protection. Essentially, this class is similar to Type I class I except that the surface is mechanically burnished prior to the last coating application to obtain sacrificial corrosion protection. This class will provide the minimum corrosion products. Coatings will protect parts with faying surfaces, joints and seams of similar and dissimilar basis metal. Such parts with faying surfaces of dissimilar metals would not require tape or sealing compounds for precluding the galvanic corrosion effects of dissimilar basis materials.
The Type I, class 4 coating is intended to provide the same protection against corrosion as Type I, class 2. The coating is used to match the matte finish, polished or buffed surfaces of surrounding corrosion resistance steels or other materials. This coating can be polished to a mirror finish if desired. For compressor blades and vanes, this class coating may be used, as certain types of burnishing operations will improve the surface finish of the final part when polished.
The Type II coating is intended to provide oxidation and corrosion protection of ferrous and ferrous base alloys, corrosion resistance steels and nickel base alloys. It is highly effective in salt and acid vapor atmospheres. Parts with this coating must be capable of withstanding the 1450 to 1520°F (786 to 828°C) fusion temperature without deleterious effects. It affords a high degree of sacrificial corrosion protection and can be used on faying surfaces of dissimilar metals. Essentially, there is no difference in properties between the two classes of this type coating except that the surface is mechanically burnished or buffed to improve finish of the part.
The Type III coating is intended to provide oxidation and corrosion protection of the same basis metals as with Type II, with titanium and its alloys added and for the same applications. It affords a high degree of sacrificial corrosion protection as does Type II. Faying surfaces are covered and protected as well as weldments. Essentially, there is no difference in properties between the two classes of this type coating except the mechanical post treatment improves surface finish.
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