Anticorrosion Properties

Water resistance alone does not ensure that grease will protect bearings or other mechanisms against moisture corrosion. Methods for assessing rust prevention by grease have been described (ASTM D-1743, IP 220). 

In the former method (ASTM D-1743), a tapered roller bearing is packed with grease and after a short running-in period is dipped and stored above distilled water. The bearing is then cleaned and examined for corrosion. In the latter method (IP 220), the grease is tested in a ball bearing under dynamic conditions. The bearing is run intermittently in the presence of distilled water and at the end of the test is rated for corrosion. 

The lubricating fluids that can be thickened to form grease vary widely in composition and properties (Chapter 12). 

An analytical procedure (ASTM D-128) is available for the separation of grease into its component parts and their measurement. Spectrographic methods, such as flame photometry (ASTM D-3340), may also be used to determine the metal present as soaps or the wear elements in used grease, in conjunction with separation techniques to measure and identify the various types of fats, lubricating fluids, or additives present. The simpler tests that are more likely to be quoted are ash content, acidity and alkalinity, water, and dirt content. 

Minerals and inorganic salts are determined as ash by ignition (ASTM D-128, IP 5),and the data include the bulk of clay-type nonsoap thickeners. The method includes a rapid routine method and a procedure in which sulfuric acid is added to avoid loss of the more volatile oxides, and the result is reported as sulfated ash. 

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Sulfonic acid salts have found widespread use in the area of corrosion inhibition. Lubrizol Corporation produces a wide variety of sulfonic acids, particularly in the form of magnesium salts, for use in lubricant formulations, anticorrosion coatings, greases, and resins (146,147). Petroleum sulfonates are used in epoxy resin elastomers to improve anticorrosion properties of coatings and sealants (qv) (148,149). 

Reaction of TYZOR TPT with polyperfluoroalkylene ethers containing a carbonyl group produces a complex that is an excellent surface-treating agent, imparting improved surface wettabiUty and anticorrosion properties to metal surfaces (144). These complexes can be used by themselves, or as additives to perfluoropolyethers as vacuum pump oils, lubricant oils, or mold release agents. 

The anticorrosion properties of lanolin have been utilized over a considerable period, and the product has the status of a temporary corrosion inhibitor (186) (see Corrosion and corrosion control). There is probably potential for greater use of the poorer grades of lanolin for long-term storage and protection of machine parts. Other uses have been reviewed in detail (182). 

Miscellaneous Derivatives. Fimehc acid is used as an intermediate in some pharmaceuticals and in aroma chemicals ethylene brassylate is a synthetic musk (114). Salts of the diacids have shown utUity as surfactants and as corrosion inhibitors. The alkaline, ammonium, or organoamine salts of glutaric acid (115) or C-5—C-16 diacids (116) are useflil as noncorrosive components for antifreeze formulations, as are methylene azelaic acid and its alkah metal salt (117). Salts derived from C-21 diacids are used primarily as surfactants and find apphcation in detergents, fabric softeners, metal working fluids, and lubricants (118). The salts of the unsaturated C-20 diacid also exhibit anticorrosion properties, and the sodium salts of the branched C-20 diacids have the abUity to complex heavy metals from dilute aqueous solutions (88). 

The more common bacteria found in infected soluble oil systems can degrade the inhibitors, emulsifiers and mineral oil components. They cause a loss of anticorrosion properties, increase of acidity and deterioration of the emulsion. These bacteria thrive in well-aerated systems, and are termed aerobic. 

In recent years, the spraying process has been adapted for hard facing, using the chromium-nickel-boron alloys which have become known as Colmonoy. More recently still, the cobalt-base Stellite alloys have also been used. These materials in powder form are sprayed on to the surface in the usual way. The deposit is afterwards heat treated by a torch, so that fusion takes place. The process is often known as spray-welding. Such coatings are primarily used for hard facing under wear conditions, but as the Anal surface is nickel-chromium or cobalt-chromium they exhibit very high anticorrosive properties. 

There are many reasons why pigments are added to coatings to make paints. The pigment imparts opaqueness and color to the coating. It can adjust the gloss or shininess of the coating, improve the anticorrosive properties of the coating, and help to reinforce the binder. 

Lightweight metal with anticorrosive properties combines with iron and aluminum to form metal alloys useful in manufacturing. 

The deposits of zinc on different metals, especially on steel, have special relevance because of their anticorrosive properties by... 

Stability properties resistance toward light, weather, heat, and chemicals, anticorrosive properties, retention of gloss (see Section 1.4)... 

Commonly used (good anticorrosive properties) o Anticorrosive properties depend on the formulation — Seldom used... 

The mechanism of the action of zinc phosphate is shown in Figure 69. Zinc phosphate dihydrate pigment is hydrated to the tetrahydrate in an alkyd resin binder [5.84], The tetrahydrate is then hydrolyzed to form zinc hydroxide and secondary phosphate ions which form a protective film of basic iron(III) phosphate on the iron surface [5.80]. The anticorrosive action of zinc phosphate depends on its particle size distribution. Micronization improves the anticorrosive properties [5.85]-[5.87], The effect of corrosion-promoting ions on the anticorrosive properties of zinc phosphate is described in [5.88], [5.89],... 

The compositions and properties of some commercial multiphase anticorrosive pigments are listed in Table 43. Their anticorrosive properties in various binders are shown in Table 39. 

Its anticorrosive properties in various binders are given in Table 39... 

The anticorrosive properties of this class of pigments depend on ... 

The anticorrosive properties of calcium plumbate are inferior to those of red lead [5.114], Calcium hydroxide is formed as a hydrolysis product when water penetrates through a primer that contains calcium plumbate. The pH at the metal surface then increases to ca. 11-12 which inhibits corrosion. 

Originally, only fine powders used for coloring various media were defined as pigments. This definition has been expanded to include many powdery materials, e.g., metallic powders and powders having magnetic or anticorrosive properties, which are intentionally dispersed (not dissolved) into media to increase value and/or impart some special properties,... 

Whereas zinc oxide was originally used as a pigment, its most important modem application is to aid in vulcanizing synthetic and natural rubber. Paint and coating industries use zinc white mainly as an additive to improve anticorrosion properties, mildew resistance, and durability of external coatings. 

Theoretical calculations predict anticorrosion properties for 4-arnino-1,2,3,5-thiatriazoles <2005JMT61>. 

Similarly to bis(octylphenoxy)dithiophosphate, one can obtain other bis(alkylphenoxy)derivatives of dithiophosphoric acid. As mentioned above, these ethers are veiy efficient additives for lubricant oils used in intensive operation engines. An addition of 1-5% of these substances greatly increases thermal oxidative stability and anticorrosion properties of lubricant oils and reduce varnish formation in engines. 

Inks— Mannich bases derived from naphthol and benzotriazole are additives providing dispersant and anticorrosion properties for intaglio printing and ballpoint pen inks, respectively. 

Chromium has long been prized for its beauty as a polished coating on metals (see photo) and for its anticorrosive properties in stainless steel and other alloys. In trace amounts, chromimum (HI) is an essential nutrient. Chromium (VI) in the form of sodium dichromate is widely used in aqueous solution as a corrosion inhibitor in large-scale industrial processes. See margin note on page 574 for more details on chromium. 

Electroless Ag-PTFE composite coatings were prepared on stainless steel substrates for the prevention of biofilm growth.87 The anticorrosion properties of Ag-PTFE composite coatings were investigated in 0.9% NaCl solution. The results showed that the corrosion resistance of the Ag-PTFE composite coating was superior to that of stainless steel. 

Comprehensive review of the structural aspects and anticorrosion properties of passive films on metals and alloys... 

Owing to their anticorrosive properties TPs (e.g., 205) serve as rust inhibitors in lubricants for magnetic recording materials (95JAP(K)07/65352) or in chemical-mechanical polishing systems (02JAP(K) 134442). 

The tribological properties of three novel anions ILs were studied. Phosphate ILs were synthesized and evaluated as lubricants for steel/steel sliding pairs [91,92]. It was found that alkyl imidazole phosphate ILs exhibit excellent lubrication and anticorrosion properties (Fig. 9.16). This was attributed to their reaction with the friction surface to generate a FePO -alkyl imidazole protective film which can significantly reduce friction and wear. 

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