Wear inhibitors

Walker, R. M., et al., Ceramic Coatings as Wear Inhibitors in Slow-Rolling Contacts, Proc. Int. Conf. on Metal. Coatings and Thin Films, San Diego, CA (Ap. 1993)... 

A field test was conducted to evaluate the valve train wear in a 2.3 L OHC (over-head cam) engine with new technology crankcase lubricants these oils also passed the V-D test (Haris and Zakalka, 1983). Oils formulated with secondary alkyl zinc dithiophosphate (ZDDP) wear inhibitor provided significantly better wear protection than two different primary alkyl ZDDPs. Secondary alkyl ZDDP demonstrated good wear protection at a phosphorus content as low as 0.07 (wt%). 

Certain oil additives are produced by reacting hydrated limes with alkyl phenates or organic sulfonates. The resulting calcium soaps act as wear inhibitors, help to prevent sludge build-up and neutralise acidity from products of combustion. 

P, M and L are the pol3mier, metal and lubricating medium P, 1/, Cl are the frictional factors, i.e. pressure, velocity and the presence of Cl in the friction zone TCRP are the tribochemical reaction products. The latter can fulfill the function of wear inhibitors (WI) during physical-chemical interactions with the inhibitor on the metal friction surface or form neutral wear products (NWP) affecting neither corrosion nor friction. The task is how to transform these products into useful ones during friction. 

V.A. Goldade, V.A. Struk and S.S. Pesetsky. Wear Inhibitors of Metal-Polymer Systems. Moscow, Khimiya, 1993. 

Wear inhibitors (WI) are substances able to alleviate mechanochemical wear in friction joints [18]. The notion of WI helps to generalize numerous means of fighting corrosion in machines and mechanisms independently of their friction joint design and composition. 

We know two major competing directions of tribodestruction of heterocyclic polymers i) decomposition of a heterocycle (quinoxaline, imide, oxa-diazole or others) as a result of the destruction of weak links of the backbone chain leading to a drop in the polymer molecular mass until the formation of low-molecular products and ii) the reactions resulting in formation of a branched and cross-linked polymer structure [97, 104-106]. Low-molecular products of macromolecular destruction (both gaseous and oligomer) may serve as tribochemical lubricants that reduce the friction coefficient and function as wear inhibitors. 

Thus, it is evident that tribochemical reactions are critical for the formation of antifrictional films on the friction surface of the metal counterbody. A new phase (transfer film or third body) functioning as a wear inhibitor protects metal parts first of all from fatigue failure as well as against adhesive and mechanochemical wear. 

Analogous cycles are observed in the polyacetal-steel and polyolefin-steel friction pairs. Physical-chemical processes can exert a favorable effect on the metal-polymer friction pair as well. For instance, metal-containing compounds of copper stearate and oleate types are formed in the contact zone as a result of tribochemical reactions when CFD copolymer rubs against copper. These compounds retard thermally destruction processes in CFD, serving as wear inhibitors (WI) for this system. 

It is quite apparent that Cl are able to function as efficient wear inhibitors and contribute to extending the lifespan of metal-polymer friction joints. 

MiscelUneous. Mahc acid is used in pharmaceuticals (qv), cosmetics (qv), dentifrices (qv), metal cleaning, electroless plating (46), wash-and-wear textile finishing (47—49), for stabilization of heat-sensitive copying paper (50), as an inhibitor of gelation, livering, and agglomeration in cellulose nitrate Hqueurs, and in many other appHcations. 

Optimum surface roughness usually is 0.05—0.5 pm a very smooth surface contains very Htde lubricant within its depressions, whereas rough peaks penetrate the lubricant to promote wear. Improved corrosion resistance may be obtained with a suitable subcoating surface conversion treatment or by inclusion of inhibitors in the coating. 

Water plays a primary role in corrosion of the metal walls of tanks and pipes (17), and increases the tendency for high speed pumps to produce wear particles and to exhibit shortened life. Formation of corrosion products can be controlled by addition of corrosion inhibitors, a mandatory additive in military fuels. However, corrosion inhibitors may also degrade other fuel properties and adversely affect ground filtration equipment. Thus they are not generally acceptable in commercial fuels where rigorous attention is given to clean and dry fuels upon aircraft fueling. 

Poisons ndInhibitors. Catalyst poisons and inhibitors can come from the fuel, the lube oil, from engine wear and corrosion products, and from air ingestion. There are two types of catalyst poisons one poisons active sites, the other is a masking agent. 

Another major cause of wear is the chemical action associated with the inevitable acidic products of fuel combustion. This chemical wear of cylinder bores can be prevented by having an oil film which is strongly adherent to the metal surfaces involved, and which will rapidly heal when a tiny mpture occurs. This is achieved by the use of a chemical additive known as a corrosion inhibitor. 

The main function of most lubricants is to reduce friction and wear between moving surfaces and to abstract heat. They also have to remove debris from the contact area, e.g. combustion products in an engine cylinder, swarf in metal-cutting operations. Sometimes they have to protect the lubricated or adjacent parts against corrosion, but this is not a prime function of most lubricants. On the other hand, many lubricants do contain corrosion inhibitors and some lubricating oils, greases, mineral fluids and compounds are specially formulated to prevent the corrosion of machinery or machine parts, particularly when these components are in storage or transit. These temporary protectives are described in Section 17.3. 

Thiazide and related diuretics, loop diuretics, potassium-sparing diuretics, carbonic anhydrase inhibitors, triamterene Avoid exposure to sunlight or ultraviolet light (sunlamps, tanning beds) because exposure may cause exaggerated sunburn (photosensitivity reaction). Wear sunscreen and protective clothing until tolerance is determined. 

MAOb inhibitors include selegiline and rasagaline. They may provide mild symptomatic benefit for those patients who choose to delay dopaminergic medications. Combining selegiline or rasagaline with levodopa in early treatment may delay motor complications. In patients with advanced disease, they decrease off time and improve wearing-off symptoms in patients with motor fluctuations. 

Zinc dialkyl/diaryl dithiophosphates are widely used as antiwear additives in engine oils to protect heavily loaded engine parts from excessive wear. They are also used as antiwear agents in hydraulic fluids. The salts are effective oxidation and corrosion inhibitors, they also act as detergents. During friction, these salts form anion-radicals that are successfully cleaved (Kajdas et al. 1986). 

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