The present invention is related to the development of a mixture to accommodate nano-dimensioned hexagonal boron nitride in Zn, Zn-Ca, Fe and Mn phosphate coating, to the application of this mixture, and to the products coated with Zn, Zn-Ca, Fe and Mn phosphate accommodated with hexagonal boron nitride.
Phosphate coating was primarily used for protecting steel against corrosion or for ensuring better adhesion of plastic coating; later on, it started to be used for forming metals or used as lubricant by absorbing oil into its porous structure in order to prevent from friction.
Zn, Zn-Ca and Fe phosphate coating, in general, keeps the oil and forming chemicals used in metal forming processes through extrusion and rolling on the surface. It ensures that forming chemicals bleed as the metal is reformed. The metal will flow easily in these conditions, and the lifetime of the mould will increase since the metal does not stick to the mould.
Mn phospate started to be used to prevent steel corrosion in 1940s. Later on, it became a coating used for lubricating. Due to its hard and porous structure locking the oil inside, it started to be used as the most appropriate coating for corroding environments in need of lubricating. Non-lubricating metal-to-metal contact causes high temperature and high pressure. Such metal-to-metal contact in non-lubricated environments results in corrosion, abrasion, and breakdown of the parts. Here, the importance of preventing metal-to metal friction comes to-the coating stops metal-to-metal contact, and therefore it is commonly used in various sectors such as automotive, refrigerator, air-conditioning compressor, etc. for coating machinery parts, gears, beds and ball-bearings, rings, roller bearings, shafts and similar parts that move one on top of another.
Mn phosphate is a type of phosphate coating bearing the best possible features for abrasion and friction. How to apply Mn phosphate coating is described broadly in patent documents numbered GB 812.095 and GB 1.417.269.
U.S. Patent No. 2004/0062869A1 points out that Mn phosphate coating cannot respond to the recent developments, especially to the need of load for mobile parts and to the longer servicing life, and thus simple manganese phosphate coating cannot be used in certain areas anymore. In order to improve Mn phosphate coating, the coating was covered with surface film using water-based resin containing molybdenum disulfide.
U.S. Pat. No. 1,696,359 discloses application of Mn phosphate for minimizing abrasion in gears and roller bearings, and addition of lubricating phosphor components to the oil for preventing abrasion.
In U.S. Pat. No. 4,662.,67, a Mn phosphate coated compressor part is applied a lubricating film containing molybdenum disulfide, tungsten disulfide, graphite and boron nitride mixed with resin.
In U.S. Pat. No. 6,509,099, Zn phosphate coating used for steel sheets in the automotive sector is applied boron nitride layer, mixed with various types of resin, in order to facilitate forming.
Above-mentioned patents allow for application of a layer containing solid lubricant to improve the features of Mn, Zn, Zn-Ca and Fe phosphate coating. This layer that is added onto the phosphate coating is destroyed after a certain period of time due to abrasion, and the phosphate coating is revealed. Besides, additional procedures are needed for each additional layer, which increases the cost.
With the present invention, a mixture is developed for adding nano-dimensioned particles of hexagonal boron nitride, which is known as a solid lubricant, into the plating bath during the phosphate treatment. As a result of applying this mixture, nano-dimensioned hexagonal boron nitride interlays among the phosphate crystals during formation.
Hexagonal boron nitride improves the lubrication feature of the coated product because hexagonal boron nitride particles have better lubrication properties than the phosphate crystals. Having interlaid among the phosphate crystals, the nano-dimensioned hexagonal boron nitride will endure for a longer period of time compared to the other methods, and no additional process will be required since it is applied during the phosphate coating.
This present invention provides the following benefits:
This present invention provides for preparation of a mixture to add hexagonal boron nitride into the Zn, Zn-Ca, Fe and Mn phosphate coating baths. This is a water-based mixture containing hexagonal boron nitride of 0.2 to 10 percent by weight. Hexagonal boron nitride can be used stand-alone; but it is possible to use different additives as well. The mixture also contains, in various ratios, nano-dimensioned solid lubricants (including but not limited to molybdenum disulfide, graphite, tungsten disulfide), surfectants and wetter agents (including but not limited to non-ionic, anionic, cationic, amphoteric surfectants and wetter agents), and phosphate bath chemicals (including but not limited to phosphoric acid solutions containing alkali metal/heavy metal ions, orthophosphoric acid, manganese phosphate salts, oxidants, catalyzers, α-hydroxy acids, EDTA, NTA, DTPA glyconic acids, nickel, tungstate ions). D50 of the hexagonal boron nitride in the mixture is less than 500 nanometer. This mixture containing nano-dimensioned hexagonal boron nitride is well-mixed using mechanical and/or ultrasonic methods prior to addition into the phosphate coating bath. This mixture is added into the phosphate bath at a ratio from 1% to 50% depending on the characteristics of the coating. No other changes are done in terms of coating conditions. When the coating is completed, nano-dimensioned hexagonal boron nitride particles are interlaid among the pores of the phosphate layer formed during the coating process.
The nano-dimensioned hexagonal boron nitride particles among the Mn phosphate crystals are not sharp since they are very small in size. In
This present invention decreases the friction coefficient of coating surface with no additional procedure by placing nano-dimensioned hexagonal boron nitride among the Mn, Zn, Zn-Ca and Fe phosphate coating layers. This improvement in the coefficient of friction as well as abrasion resistance due to placement of hexagonal boron nitride particle among Mn phosphate coating makes it possible for various sectors (e.g. automotive, white goods) to use products coated as such.
Number | Date | Country | Kind |
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2011/01163 | Feb 2011 | TR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/TR2012/000015 | 1/27/2012 | WO | 00 | 7/17/2013 |