Anti-seizes

Dispersion in Rapid evaporation Limited storage Anti-seize,... 

While molybdenum disulphide lubrication is adversely affected by liquids, liquid lubrication can be improved by molybdenum disulphide. There is in fact a considerable industry based on the use of molybdenum disulphide in liquids, in dispersions, lubricating oils, greases, anti-seizes and pastes. There is an important contradiction in the fact that in many situations the lubricating action of molybdenum disulphide is either partly or completed destroyed by the presence of liquids, whereas in other situations it can provide useful lubrication benefits in a liquid medium. A great deal of effort has been applied in attempts to establish the mechanism and the conditions by which lubrication by molybdenum disulphide can occur in the presence of a liquid. 

When molybdenum disulphide is added to a grease, the effect on the flow properties depends critically on the concentration of molybdenum disulphide. Where the quantity added is high enough to cause a major change in the flow properties, the result is a product which no longer behaves as a grease, but behaves like a paste. Such materials are generally used as anti-seize compounds rather than lubricants, and they will be described in Section 13.4. 

There are three main types of application for which molybdenum disulphide pastes and concentrated dispersions are used. They are used as anti-seize compounds for threaded fittings, pipes, flanges, and so on. They are also used to assist assembly, and to a lesser extent running-in, of many different types of mechanical euqipment. Finally, they are used in high-load metalforming processes. 

Pastes can be made with the same carrier liquids by simply increasing the concentration of powder to achieve a paste-like semi-solid consistency. More stable pastes are obtained by using a carrier which is inherently semi-solid, such as a grease, petrolatum (soft petroleum wax) or a semi-fluid polymer. The concentration of powder in a paste or a dispersion may be anything between 35 and 75%, depending on the application. The British military specification Def Stan 80-81/1 requires not less than 50% of molybdenum disulphide in a mineral oil grease for an anti-seize and anti-scuffing compound for use up to 250 C. This is probably a fairly typical level for anti-seize use. 

In other words, this one material was intended to meet the requirements of anti-seize and anti-scuffing compounds, pre-assembly, and metalforming. A primary objective of the standard was obviously to simplify supply in a relatively tightly-controlled economy. In more competitive economies a very large number of... 

Table 13.10 Some Commercial Dispersions and Pastes for Anti-Seize, Assembly and Metalforming (Some of these may now be obsolete)...

Molypaul Polypaste 300 Grease-based Anti-Seize... 

Several publications have described the use of molybdenum disulphide pastes for the lubrication of screw threads. This is an application in which the paste assists assembly and subsequently acts as an anti-seize. The critical factors in screw or bolt assembly are the friction between male and female thread and between bolt-head and workpiece, and their effect on the relationship between assembly torque and bolt tension (clamping force). The stiffness and integrity of a bolted assembly are determined by the bolt tensions, but since it is impracticable to measure bolt tension directly, the required bolt tension is controlled by the torque applied to the bolt or nut. However, the relationship between assembly torque and bolt tension is determined by head friction and thread friction. If the friction is reduced, the required bolt tension will be obtained at a lower assembly torque. 

One other area in which the use of molybdenum disulphide may be undesirable for pre-assembly or anti-seize use is when nickel alloys are used in critical applications, especially at high temperatures. Such alloys are extensively used in aviation gas turbine engines, and there have been cases in which serious failures of gas turbines have been attributed to the effect of molybdenum disulphide-based lubricants on high-temperature components Provided these two hazards are kept in mind, molybdenum disulphide dispersions and pastes are of great value as antiseize compounds and as assembly aids. 

Isopropyl alcohol 10-20 Dry film mould lubricant, anti-seize, electrically-conducting coating... 

The degree of improvement in a few years is clearly indicated by the marked reduction in the number of publications about corrosion after 1976. With the elimination of graphite and of excessive ball-milling, and the incorporation of corrosion inhibitors, it should now be possible to use molybdenum disulphide in bonded films, composites, greases or anti-seizes with confidence that no corrosion problem will arise, although commonsence precautions should always be taken ... 

Screw threads, rivets, or fasteners in air to 150°C Molybdenum disulphide paste anti-seize... 

Installation Manual If available, most likely will not reflect current installation techniques. Basic information such as guidance on fastener installation may not be defined (torque, anti-seize or dry etc). Available, most likely will reflect current installation techniques. Installation method can be tailored to contractor s preferred installation methods. 

Table I. Summary of Qualification Requirements for One Type of Anti-Seize and Sealing Thread Compound for Use in Aircraft Oxygen Systems, Mil-T-5542B [3]...

Military Procurement Specification, QPL 5542-6, "Thread Compound. Anti-Seize and Sealing, Oxygen Systems," U. S. Government Printing Office (July 12, 1954). 

Rocketdyne, Division of North American Aviation, "Lubricants, Anti-Seize Compounds, and Gasketing Type Sealing Compounds for Rocket Engines," Process Specification No. RA 0112-002, Canoga Park. California (November 12, 1958). 

Convair-Astronautics, "Thread Compounds Anti-Seize and Sealing, Gaseous and Liquid Oxygen Systems," Report No. 0.73.001, San Diego, California (January 12, 1957). 

Douglas Aircraft Company, "Anti-Seize Lubricants for Mating Parts," Process Specification No. 1.22, Santa Monica, California (March 27, 1958). 

Add to maintenance procedures to inspect and clean regularly. Add use of anti-seize compound to operating procedures. Add to quarterly inspection to verify all gaskets, 0-rings, and proper seals are in correct position. Verify that each gasket fits over shoulder and end caps. Avoid hammering seal palate into valve assembly. 

The noble metals, i.e. gold, platinum, palladium, and rhodium, and the corrosion-resistant metals, i.e. chromium, nickel, tin, tin-lead solder, and titanium, require no finish other than cleaning. Soldered joints should be protected with a moisture-proofing compound or coating. Corrosion-resistant (or treated to resist corrosion) minor devices (fasteners, etc.) should be used. Fasteners should be treated with zinc chromate, zinc chromate paste, or graphite-free dry-film anti-seize compound. 

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