PT1963543E - A steel wire rope for use in a drive system - Google Patents

Abstract

A steel wire rope for use in a drive system such as found on a sliding vehicle door or window elevator is revealed. Particular about this rope is that it has a remarkable corrosion resistance in combination with a reduced wear of guiding pieces around which the wire rope is guided. The corrosion resistance is obtained by spreading magnesium oxide particles over the zinc or zinc alloy coated steel wires and bringing those particles in contact with the coating. The reduced wear is obtained by spreading fine abrasive particles over the coating. The spreading and contacting can be achieved by means of a liquid carrier such as an aliphatic mineral oil that is commonly used as the lubricant for such steel wire ropes. The magnesium oxide ensures an equal or better corrosion resistance even when reducing the thickness of the zinc coating. Reducing the thickness of the zinc coating increases the strength of the steel wire rope, while maintaining the diameter of the cord. The abrasive particles ensure a polishing of the wire leading to a smoother surface and reduced wear of the guiding pieces.

Description

- 1 - ΡΕ1963543

A STEEL CABLE FOR USE IN A TRANSMISSION SYSTEM "

Field of the Invention The invention relates to the field of steel cables and in particular to steel cables which have to withstand corrosive environments during operation. These types of steel cables can be found in many drive systems, such as a car door window lift, a sliding door drive system, a canvas roof unit, a door drive system of a garage, or a power cable to name but a few. The invention provides a more corrosion resistant type of cable, while providing good fatigue strength and improved friction properties.

Background of the invention

Steel cables are in many cases the preferred means of transmitting force and displacement (ie work) through a distance between meters and kilometers at a reduced cost. The cables can be made to be very flexible - so that the cable can accommodate small pulleys - using cables with finer diameters in their construction. When fabricated with cold drawn steel wire, the strength of the cable can be increased thereby allowing the 2 ΡΕ1963543 transmission of higher forces. In addition, the modulus of elasticity is close to that of the steel and the elongation of the cable can be minimized thereby eliminating the slack of the drive system. The cables may be designed to withstand repeated twisting, flexing or extension movements occurring in such drive systems. In fact, steel cables are reliable because the fatigue limit can be accurately predicted through tests that simulate the actual use of cables. Finally, the steel cables have a favorable coefficient of friction with respect to wear parts, a property that, in many cases, allows the replacement of bending pulleys by fixed cable guides with considerable reduction of costs in the drive system as a consequence .

Unfortunately most steels tend to rust when subjected to conditions that increase corrosion (such as outdoor use, but also inside an elevator shaft, or inside a car door). Corrosion is detrimental in this regard as it can drastically reduce the anticipated level of fatigue leading to premature fatal fractures. This mechanism is known in the field as " corrosion fatigue ", ie, the phenomenon of fatigue that occurs when the cable is subjected to a dynamic load in a corrosive environment. Some standard solutions to reduce this corrosion are known to qualified persons: - Stainless steels that are less prone to corrosion (such as AISI 306, AISI 314) can be used. Unfortunately, 3 ΡΕ1963543 such steels often only perform well in static corrosive applications, ie when there is no dynamics involved. When the cables are repeatedly used in pulleys, the oxide protective coating that forms on stainless steel is continuously worn away leading to excessive frictional corrosion of the filaments and life in the lower fatigue. - Perhaps the oldest solution is to use individually wires coated with a protective layer. In order not to negatively influence the other properties of the steel cable, the coating is preferably metallic. Most applications in this regard are zinc or zinc alloy coatings which are applied to the steel wire through a hot dip process. Intermediate alloy layers are formed in the hot soaking ensuring a good adhesion of the coating to the steel wires. Such coatings provide the steel with sacrificial protection against corrosion. The encapsulation of the cable in a polymer is also a known technique. Such encapsulation must withstand the dynamics of the drive system to prevent corrosive atmosphere from reaching the steel surface. WO 03/044267 describes such a cable. The solution offers excellent corrosion protection in combination with excellent fatigue properties, but is a little stiffer, does not have such good friction properties and is more expensive. or gels - The application of oils, fats, masses 4 ΡΕ1963543 corrosion inhibitors. The masses must allow the steel cable a number of properties and are in many cases a compromise between different properties (cost, environmental performance, fatigue, etc.). An example can be found in US 6106741. The current state of the art for cable drive system is therefore dominated by zinc coated cables or zinc alloys which are immersed in a lubricant. The thickness of the zinc or zinc alloy coating is chosen to withstand a certain number of hours in a corrosive environment. Such corrosion tests are widely known in the field as the ISO 9227 standard (national equivalents are ASTM B117 or DIN 50021). Here samples obtained from steel cable manufacturers are hung in closed chambers with a suspension mist maintained at a relative humidity of 100% at a temperature of 35 ° C. The atmosphere in the chamber is saturated by circulating water spray containing 5% by weight NaCl. As described in ISO 9227. The progress of corrosion is regular (for example, every 24 hours) and visually monitored and classified into a number of grades ("rust spots light brown", "brown rust spots" light brown rust spots, " dark brown rust spots " and " 5% dark brown rust surface cover "). In what follows the number of hours of saline mist that has been withstood in this test is up to " Rust spots 5 ΡΕ1963543 dark brown " appear in the sample. At present the cables must support a minimum of 72 hours of salt spray to be accepted in the automotive industry. The lubricant is chosen in order to optimize the life to the fatigue. Lifetime fatigue estimates can be obtained through dedicated test procedures that simulate the real-life use of the cable in drive systems. Thus, there are a number of proprietary test benches available to determine life to fatigue. A test available to the public is the MIL-W-8342O-standard which was (and still is) widely used for "aircraft cables" testing.

In the industry there are constant drives to use cables of lesser thickness of equal or greater strength in order to reduce the size of the transmission systems, increasing the protection against corrosion as well as the resistance to fatigue. With known zinc coatings or zinc alloys occurs in a conflict between strength and corrosion protection. As the corrosion protection of the coating is approximately proportional to the thickness of the coating, a minimum coating thickness must be maintained in order to meet the corrosion requirements. However, by using thinner wires, the coating occupies an increasing amount of cross-sectional area of the cable. As the coating does not increase the strength of the wires, thinner cables compared to their thicker counterparts lose 6 ΡΕ1963543 relatively resistance due to this cause. WO-A-03/048403 discloses a process for improving the corrosion resistance of substrates, such as substrates of galvanized steel wires, comprising coating the substrate of galvanized steel with a solution containing oxide nanoparticles. DE-A1-4202625 discloses a metal product coated with a layer of zinc having a thickness of 10-30 micrometers. A more resistant coated metal product is obtained by the addition of MgO to the zinc coating in an amount of 10-5000mg / m 2. EP-A1-1508479 discloses a steel product coated with a layer of zinc having a weight of 10-100 g / m 2. A more corrosion resistant steel product is obtained by the addition of MgO to the zinc coating in an amount of 10-100 g / m 2.

Summary of the Invention. It is therefore a first object of the invention to provide a steel cable that overcomes the problems of the past. More in particular, it is an object of the invention to provide a steel cable which combines good corrosion resistance without losing resistance. It is an additional object to provide a steel cable with improved friction properties. The inventors have sought a particularly simple 7 ΡΕ1963543 corrosion inhibitor adapted to the specific use of cables in drive systems which is efficient, inexpensive, environmentally friendly and easy to apply: a further object of its invention.

According to a first aspect of the invention a metal cable is provided, which is intended for use in a drive system. Such cable types have a diameter of less than 5 mm, although diameters below 3 mm are preferred, whereas diameters of 2 mm and 1.5 mm are currently more preferred. The inventors believe that the trend for smaller diameter cables will continue and predict that 1mm diameter cables will be possible in the foreseeable future. The metal cable is manufactured from zinc-coated or zinc-alloy steel wire. The steel used to produce this wire is - as high strength is required - a high carbon steel. Such steels have compositions according to the following lines: a carbon content between 0.35% and 1.15%, preferably between 0.60% and 1.00% carbon, a manganese content between 0.30% and 0,70%, silicon content between 0,10% and 0,60%, a maximum sulfur content of 0,05%, a maximum phosphorus content of 0,05%. Micronations with particular elements such as chromium, nickel, vanadium, boron, cobalt, copper, molybdenum, are not excluded in amounts ranging from 0.01-0.08%, as these alloys can help achieve higher levels of strength. - 8 - ΡΕ1963543

Particularly popular coatings for these steel wires are: - A technically pure zinc coating in which the inevitable impurities are also included. An intentional zinc alloy coating of which the following are particularly contemplated: Zinc and aluminum alloys, such as those comprising 2-12% Al and a mischmetal such as cerium or lanthanum, the remainder being zinc. These are particularly preferred because of their anti-corrosive properties (see for example EP 0 550 005 B1). Zinc and iron alloys, such as those containing 0.3-1.5% Fe or those containing 15 -25% Fe, the remainder being zinc. Iron may originate from the steel substrate itself. • A zinc and tin alloy. This is a coating to which favorable frictional properties are attributed (see, for example, DE 195 12 180 A1). Zinc and nickel alloys such as those containing 20-30% nickel, the remainder being zinc.

Note that the wire coating is generally made of an intermediate diameter steel wire which is subsequently drawn into smaller diameters through a series of matrices. During the drawing the tensile strength of the wire gradually increases, an increase which is declared for high carbon steel wire as contemplated in the present application. Typically, the steel wire 9 ΡΕ1963543 has a tensile strength greater than 1750 N / mm 2, typically above 2500 N / mm 2, or preferably above 2750 N / mm 2, or even in excess of 3000 N / mm 2. Such high tensile strengths are required to further reduce the diameter of the steel wire. The wire diameters for this type of cable are rarely greater than 0.25 mm, and preferably less than 0.22 mm, or preferably below 0.15 mm. The use of many small diameter wires results in a more fatigue resistant steel cable than a cable with fewer wires having a larger diameter. The wire is gathered into strands which can, in turn, be gathered into steel cable. Common typical settings on the branch are 7x7, 7x19, 19 + 8x7, 19W + 8x7, 7x8, 8x7, 8x8, 19 + 9x7, Ix3 + 5x7 to name just a few. For example the formula 7x8 designates a cable composed of seven strands each composed of 8 wires. The cord consists of a core around which outer wires are helically twisted with a particular pitch. Six of said strands are twisted around a central core, again with a defined pitch. The diameters of the outer strands are preferably chosen so that they easily fit around the web. In the same way the diameter of the web can be chosen so as to be adapted to the diameter of the outer strands. The strands can be produced layer by layer by twisting wires around intermediate strands leading to an exemplary configuration of a web surrounded by six wires surrounded by 10 ΡΕ1963543 by twelve wires leading to a 1 + 6 + 12 configuration which is reduced for a 19-wire cord. A special case is where the wire diameters are chosen so that they fit perfectly together, as in a Warrington configuration (as in the 19W + 8x7 configuration core). All 19 wires are then twisted with the same pitch. Sometimes the strands are compacted before the twist of the cable and even complete strands are compacted. Sometimes a fiber replaces the soul. The inventive idea of this application is equally applicable to all these variations. Typically, the amount of coating on the wire is expressed in grams of coating per square meter of wire surface. As the coating does not increase the strength of the cable, it should be as thin as possible without compromising corrosion resistance. Conventional coating amounts are - the number in parentheses refers to the average thickness of a corresponding zinc coating having a density of 7.14 kg / dm 3 - minimum 30 g / m2 (4.2 μιη). However, lower amounts such as less than 25 g / m2 (3.5 μπι), or less than 20 g / m2 (2.8 μπι), or even as low as 15 μg / m2 (2.1 μπι) are preferred for this inventive steel cable. The inventors believe that acceptable corrosion results could be obtained with zinc coatings directed to 5 g / m2 (0.7 μπι).

Although in principle there is no limitation to the type of process used to coat the wires, hot dip processes are preferable because they provide a solid coating welded to the steel. Due to the hot immersion, a layer of alloy will form between the steel and the coating which provides additional protection to the steel.

Particularly preferred from the point of view of strength and fatigue is the coating as described in EP 1 280 958 B1. There is a zinc coating having a reduced thickness 2 of less than 2 micrometers (14.3 g of zinc per m of wire) even the zinc-iron alloy layer is described in conjunction with the associated process for coating the wires. Such wire has a reduced zinc thickness, which is conducive to obtaining a greater breaking stress of the cable. In addition, the roughness of the zinc to the steel transition layer is greatly reduced resulting in improved fatigue. Unfortunately, the coating itself does not sufficiently protect against corrosion.

However, the inventors have found that reduced corrosion resistance can be compensated for by the use of a corrosion inhibitor applied via a liquid carrier. To their surprise, they found that a very simple compound of magnesium oxide (MgO) was most suitable for this purpose. Magnesium oxide (MgO) should be finely dispersed in the carrier. The carrier only serves to distribute the magnesium oxide evenly over the wire surface: the particles must come into close contact with the wire coating. The liquid carrier may remain in place or may evaporate: it has been found that the positive corrosion inhibiting effect remains. Magnesium oxide causes 12 ΡΕ1963543 to allow the use of thin zinc coatings, implying advantages of higher strength and better fatigue, maintaining and even improving corrosion resistance. Mutatis mutandis, magnesium oxide provides greater security against corrosion when used in zinc coated wires as currently used. Magnesium oxide (MgO) is a very common product that can be obtained through a number of different processes. The first way is by heating magnesite (magnesium carbonate, a natural mineral deposit) in the presence of oxygen. The second process uses brine containing MgCl 2 which is first converted to Mg (OH) 2 for purification by wet precipitation, followed by calcination to remove the water. The latter process is preferred. The resulting magnesium oxide (MgO) can be classified to different degrees: 1. "Molten magnesium oxide" is calcined MgO which was heated in an electric arc furnace at temperatures above 2750 ° C. It is the most stable and strongest of all types of magnesia. 2. " Deep Calcined Magnesium Oxide " was heated to temperatures between 1500 ° C and 2000 ° C and has an area of less than 0.1 m2 per gram. 3. " Strongly Sintered Magnesium Oxide " was heated to temperatures between 1000 ° C and 1500 ° C and has a surface of 0.1 to 1.0 m2 per gram. 4. " Lightly sintered magnesium oxide " was heated to ΡΕ1963543 at 700 and 1000 ° C and has a surface area of 1.0 to 250 m2 per gram. The " lightly sintered " is the preferred degree, while the " heavily sintered " is less widely used. The grade " thoroughly calcined " is difficult to disperse and therefore less desirable. The " molten magnesium oxide " is too inert to be useful.

As the carrier, an aliphatic mineral oil is preferred. Aliphatic mineral oils are typically used to improve the fatigue life of steel cables by reducing friction between the wires as they are bent into a pulley or a wear part. As will be applied to the steel cable, however, they may conveniently be used as a carrier for the dispersion of magnesium oxide. Other possible liquid carriers are paraffins or in particular isoparaffenes which are known to readily evaporate. The corrosion protection effect of magnesium oxide (MgO) is immediately apparent even when only small amounts are applied to the surface of the zinc or zinc alloy coating. In fact, in a minimum of 100 mg of MgO per square meter of wire surface, positive effects on the number of hours survived by the salt mist test can be observed. This is notable in comparison to the amount of the zinc coating (present in an amount of typically 15,000 to 30 14 ΡΕ1963543,000 mg / m 2). The effects increase linearly with the amount of MgO applied on the coating of zinc or zinc alloy. An amount of 200 mg / m2 MgO is therefore preferred. Amounts greater than 1000 mg / m 2 or 2 000 mg / m 2 or up to 4 000 mg / m 2 MgO lead to even better results. At present, no leveling of positive effects has been detected. One of the inventors raises the hypothesis that - without being bound to this theory - the presence of MgO on the zinc coating suppresses the cathodic reaction (ie the electron consumption reaction) in the corrosion process. Due to this the MgO is converted into a product which improves the passivation behavior of the zinc coating. Consequently, corrosion will only begin at free MgO points. This would make MgO a cathodic inhibitor, whose efficacy increases with the amount of magnesium oxide present.

It was therefore considered important that the magnesium oxide be finely spread on the wire surface in order to obtain a uniform dispersion of the magnesium oxide flakes. This is best achieved by a finely ground magnesium oxide having a mean particle size between 1 and 100 microns, with a majority of 5-75 microns being preferred. Magnesium oxide must be in physical contact with the zinc or zinc coating layer, otherwise corrosion protection is less effective or non-existent. In order to further improve this contact, the inventors have added abrasive particles of approximately the same size (5 to 50 micrometers average particle size) of the magnesium oxide particles to the liquid carrier. The idea was that by adding this abrasive, the surface of the zinc coating is leveled, thereby facilitating the incorporation of the magnesium oxide particles. Surprisingly, they found that the addition of such an abrasive reduced wear on the polymeric guides of the drive system. Such guiding parts are generally made of hard polymers such as polyoxymethylene (POM) or polyamide (nylon 6). For a description of the test reference is made to EP 0 550 005 B1, page 14 and Figures 13, 14 and 15. The candidate presumes - without being bound by this hypothesis - that the abrasive particles not only activate the zinc coating, but also also jump the surface of the wire making it softer. As an abrasive the silicon carbide (SiC) is preferred as it is cheap and easily available in all grain sizes. Other abrasives (quartz, cubic boron nitrate, diamond, and many others) could probably work as well. Also noteworthy is that these abrasive particles do not have a negative influence on fatigue behavior of the steel cable. It has been found that between 0.1 and 10, preferably between 0.1 and 2 grams of SiC per kilogram of steel wire is more than sufficient to obtain the positive effects. It will be clear from the foregoing that the inventors have especially sought out simple chemical compounds and additives. Many of the commercial corrosion inhibitors available are for general use and are not specifically wire oriented 16 ΡΕ1963543 steel for drive systems. As such contain more than five ingredients, many of these ingredients are complex and not readily available. The inventors intentionally sought a simple solution that is above all effective, cheap, environmentally friendly and easy to implement. The number of constituents remains below five, namely: a liquid carrier (which may or may not disappear after application), magnesium oxide (MgO), silicon carbide (SiC) and perhaps some type of dispersant or "floating" 1 that can be added.

According to a second aspect of the invention, there is defined a metal wire product comprising at least one zinc or zinc alloy coated metal wire. Special on this wire is that a corrosion inhibitor is incorporated into the coating of zinc or zinc alloy as a finely dispersed solid. Preferably this corrosion inhibitor is present on the outer surface of the coating. More preferably the corrosion inhibitor is embedded, pressed against the outer surface of said coating. Preferably, this corrosion inhibitor is magnesium oxide (MgO).

According to a third aspect of the invention, a method is disclosed to protect a metal wire product. The method starts from a wire of diameter 1

Floatant in the original, the author probably refers to insulating / water repellent products. 17 ΡΕ1963543 supplied with a coating of zinc or zinc alloy. The steel and coating compositions are in line with the compositions described in the first aspect of the invention. In a drawing bench, preferably a submerged drawing bench, the wire is conducted sequentially through progressively smaller matrices, a technique common in the art. In particular on the method is that the wire entrains a finely dispersed corrosion inhibitor to one of the matrices. The corrosion inhibitor is impressed against the outer surface of the coating by the action of compression of the matrix in the wire. The corrosion inhibitor may be applied to the wire in a matrix, for example, in the input matrix (i.e., the larger) or in the output matrix (i.e., the smaller). Or the inhibitor can be supplied to the wire in two or more matrices, or in all matrices of the series. The corrosion inhibitor is supplied as a powder. In this case, the corrosion inhibitor may be blended into powdered soaps, which are common in the art of dry wire drawing of steel wire, as solid lubricants. Such a powder blend may be fed together with the wire to the matrix by passing the wire through a soap box at the die entrance. Or the corrosion inhibitor may be mixed in a liquid carrier which is entrained by the wire to the matrix inlet. It is important that the corrosion inhibitor comes into close and electrical contact with the zinc or zinc alloy coating. The corrosion inhibitor should therefore not be isolated from zinc or zinc alloy coating by entrainment of soap residues. 18 ΡΕ1963543

Preferably the corrosion inhibitor is magnesium oxide (MgO). It is preferred that the magnesium oxide powder is finely ground to pass a sieve having a mesh size of 74 μm.

Description of the preferred embodiments of the invention.

The following describes a series of laboratory scale and production environment tests that were performed on a 1.5 mm diameter 19 + 8x7 type zinc coated steel cable for use in a window lift system. The cable is of the following type: {[(0.15 + 6x0.14) 3.5s + 12x0.14] s, 5s + 8x (0.14 + 6x0.14) 4.8z}

The different levels of parentheses indicating simple operations, the subscript indexes indicating the pitch and the direction of twist. The cable has a linear mass of 9.78 g / m and a wire surface of 33.56 m 2 / km of cable. Unless otherwise noted, the cable wires were hot dip galvanized, technically pure zinc coating of about 100 g per kg of coated steel cable (ie 28 g / m 2 or an average thickness of 3.9 μιη).

In a first series of tests, a number of substances were evaluated in the laboratory. Clean cable samples were coated with compound blends with the standard aliphatic mineral oil used in the production of standard cables. Six samples each were hung in the 19 ΡΕ1963543 saline spray chamber and inspected visually on a daily basis. It was noticed the day the first dark brown spots became visible. The results mentioned in Table 1 are the mean (hSS AVG), the minimum (hSS min) and the maximum (hSS MAX) of the six samples. The compounds were present in the mixture according to the percentages indicated in the total mixture. Based on these results, MgO was selected for further investigation.

In a mixture hSS Avg hSS min hSS MAX 1 Lubricant 84 72 96 2 Lubricant + 5% Benzimidazole 116 96 144 3 Lubricant + 10% Magnesium oxide 324 312 336 4 Lubricant + 10% Zinc oxide 108 96 120 5 Lubricant + 10% Zinc carbonate hydroxide 116 96 144 6 Lubricant + 10% Magnesium hydroxide 180 168 192 7 Lubricant + 10% Hydrated phosphate zinc 84 72 96 8 Lubricant + 10% Aluminum oxide 84 72 96 9 Lubricant + 10% Magnesium hydroxide silicate 84 72 96 10 Lubricant + Magnesium Oxide + 5% Magnesium Hydrated Silicate 156 144 168 11 Lubricant + 10% Magnesium Hydroxide 156 144 168 12 Lubricant + 10% Magnesium Stearate2 132 120 144 13 Lubricant + 10% Magnesium Hydrogen Phosphate 100 72 120 TABLE 1

In a second series of laboratory experiments the influence of MgO was verified by the application of mixtures in the pickled and degreased cable with increasing amounts of magnesium oxide. Again the samples were tested in the saline mist chamber, the results of which are summarized in Table 2. The stearaat in the original, the author probably refers to stearate 20 ΡΕ1963543 hSS hSS hSS In a mixture Avg min MAX 14 Lubricant 108 96 120 15 Lubricant + 15% MgO 556 432 648 16 Lubricant + 20% MgO 716 672 792 17 Lubricant + 25% MgO 884 816 1005 18 Lubricant + 30% MgO 828 816 840 19 Lubricant + 40% MgO 1140 1032 1248 TABLE 2

In a third series of experiments, a number of mixtures were tested on an industrial scale. Steel cables with two levels of zinc coating quantity were tested: one with the standard coating of 28.0 g / m 2 wire surface and one with a reduced coating of 24.3 g / m 2. Also a different type of liquid carrier was used, namely a liquid isoparaffin wax. Low molecular weight isoparaffins readily evaporate. In this case, paraffin only acts as a distributor for magnesium oxide on the wire surface of the cable. From the result it can be deduced that the positive effects of MgO remain.

In a liquid carrier Zn (g / m2) MgO MgO hSSAvg 20 Lubricant 24.3 0 65 21 459 120 22 885 126 23 989 168 24 1138 256 25 28.0 0 85 26 72 144 27 272 248 28 504 248 29 1362 248 30 Paraffin 28.0 180 280 TABLE 3

In a fourth series of experiments, a quantity of 21 ΡΕ1963543 of silicon carbide (grain size between 8 and 32 μπι) was added to the lubricant in an attempt to activate the surface of the zinc coating for the action of magnesium oxide by light surface abrasion . Although the corrosion resistance measured in the saline mist chamber was not deteriorated or improved by the silicon carbide, another positive effect was surprisingly found. It was found that the shear wear caused by guides that are sometimes used to replace the pulleys practically disappeared: if the normal wear level was 100, the influence of the SiC reduced it to 40 and up to 25. The test was performed with a load of 120 N and a cable speed versus guide of 7.5 m / minute. The radius of curvature of the POM guide was 15 mm while the cable covers 180 ° of the part. Wear was evaluated after 5,000 back and forth cycles (i.e., 10,000 passes) where the same 430 mm of rope slides over the guide. No lubricant was added before the test.

The inventors wish to point out that the invention is equally applicable to all types of steel cable configurations and that their use is not limited to window elevator systems but to all types of drive systems (sliding doors, sliding ceilings , garage doors, curtains, brake cables, clutch cables, door locking systems, a non-exhaustive list).

Lisbon, November 18, 2011

Claims (6)

A steel cable for use in a drive system comprising steel wires coated with zinc or zinc alloy having an amount of zinc or zinc alloy which is less than 15 g / m 2, said steel wires having a diameter of less than 0.25 mm and a tensile strength greater than 1750 N / mm 2, said steel wires further comprising a liquid coating carrier comprising a corrosion inhibitor characterized in that said corrosion inhibitor is magnesium oxide, said magnesium oxide being finely dispersed in said liquid carrier. The steel cable of claim 1 wherein said liquid carrier is in the group consisting of aliphatic mineral oils, paraffenes and iso-paraffens. The steel cable of claim 1 or 2 wherein at least 100 milligrams of magnesium oxide per square meter of wire surface of said metal cable is present. The steel cable of claim 1 or 2 wherein at least 200 milligrams of magnesium oxide per square meter of wire surface of said metal cable is present. The steel cable of claim 1 or 4 wherein the average particle size of said finely dispersed magnesium oxide is between 1 and 100 micrometers. 6. A steel cable according to any one of claims 1 to 5 wherein said liquid carrier further comprises an abrasive powder having a particle size between 5 and 50 micrometers. A steel cable according to claim 6 wherein said abrasive powder is silicon carbide. A steel cable according to claim 7 wherein 0.1 to 10 grams of silicon carbide per kilogram of metal wire is present. A method of protecting a steel wire against corrosion comprising the steps: Providing a zinc or zinc alloy coated steel cable, Sequentially drawing said zinc or zinc alloy coated steel wire through successively more matrices at the inlet of at least one of said dies, a finely dispersed magnesium oxide corrosion inhibitor conducted by a liquid carrier is entrained by said steel wire to at least one said matrix and thereafter embedded therein zinc or zinc alloy. 3 ΡΕ1963543 A method for protecting a steel wire from corrosion comprising the steps: Providing a zinc or zinc alloy coated steel cable, Sequentially drawing said zinc or zinc alloy coated steel wire through successively more matrices characterized by a corrosion inhibitor of finely dispersed magnesium oxide mixed with a powdered soap, resulting in a powder mixture, said mixture being fed to the inlet of at least one of said matrices entrained by said steel wire for at least one of said matrices and subsequently embedded in said zinc or zinc alloy. The method of claim 9 or 10 wherein said magnesium oxide passed a sieve of 74 micrometer mesh. Lisbon, November 18, 2011