Method for generating a friction-optimized zinc coating on a steel component

Abstract

The present invention relates to a method for producing friction-optimized zinc coatings on steel parts. To provide a method that can be easily and economically implemented, resulting in a coating with good corrosion protection properties, good adhesion, and stable, consistently low friction values ​​even during repeated use of the steel part, including in particular repeated tightening, according to the invention, a zinc layer is first applied to the surface of the steel part by a galvanic deposition process, followed by a heat treatment at a temperature of up to 420°C to specifically form intermetallic zinc-iron phases in the galvanically deposited zinc layer in order to optimize the friction value of the steel part.

Description

Technical Field

[0001] The present invention relates to a method for producing a zinc coating with optimized friction in steel parts.

Background Art

[0002] For visual and functional reasons, steel parts are often zinc-plated for technical applications. In particular, filigree bulk parts such as steel screws and clamp sleeves are usually coated with pure zinc in a galvanic deposition process and then passivated. The basic property of the zinc layer is to protect the more noble base metal below from corrosion. Even when cracks occur, the base material is protected from attack by the anodic effect of zinc, whereby the zinc itself is oxidized and the protective effect can be ensured only for a limited time. Pure zinc is already oxidized in the atmosphere and is protected by a passivation layer.

[0003] The deposited layer system consisting of the zinc layer and the passivation layer not only provides corrosion protection but also needs to have high wear resistance, and as a result, it is necessary to maintain a certain friction coefficient against repeated tightening. However, conventional zinc-plated and passivated steel parts, such as bolts, show a significant increase and large variation in the friction value when tightened repeatedly. This is due to the layer properties and adhesion strength of the zinc layer on the steel substrate. However, in the case of electrical contact elements, when the friction value increases due to repeated tightening of the screw, the contact pressure of the conductor against the current bar decreases, the electrical contact resistance increases, and the function of the contact element is impaired.

[0004] As an alternative to electrogalvanizing, steel parts are often hot-dip galvanized or sherardized, but this is not economically feasible in some cases, for example, for steel filigree (wirework) bulk parts. Furthermore, hot-dip galvanizing results in the formation of a zinc coating and, in particular, the formation of an intermetallic (compound) zinc-iron phase with a significantly increased coefficient of friction. The coefficient of friction of hot-dip galvanized steel screws further increases significantly when tightening is repeated.

[0005] Furthermore, a method for manufacturing a zinc-plated annealed steel strip is already known from DE68912019T2. According to this method, the steel strip is first cleaned, and then at least one side of the steel strip is electroplated with a zinc coating. Thereafter, the coated steel strip is conveyed through an induction coil, where the strip is heated to a temperature of 427 °C to 510 °C, and the zinc coating is completely converted into a zinc-iron alloy coating. Finally, the steel strip is cooled. However, such a method exceeds the melting temperature of zinc in several processing steps. Therefore, this method can be applied to strips and sheets, but it has the disadvantage that it is not economically applicable to smaller steel parts such as bulk parts, screws, and clamp sleeves. Furthermore, in such a method, the zinc coating varies widely to a zinc-iron phase with an iron mass fraction exceeding 10%, which causes deterioration of the friction value, especially in the case of repeated tightening, and also causes large fluctuations in the coefficient of friction of the manufactured and coated steel parts.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Accordingly, the present invention is based on the object of providing a method for producing a zinc coating with optimized friction on steel parts, which can obtain a coating having good corrosion protection properties, good adhesion, and a stable and always low friction value during repeated use, especially repeated tightening, of steel parts, and which can be carried out easily and economically.

Means for Solving the Problems

[0008] According to the present invention, this object is solved by a method for producing a zinc coating with optimized friction on a steel part according to claim 1. Advantageous further developments are shown in the dependent claims.

[0009] In the method according to the present invention for producing a zinc coating with optimized friction on a steel part, especially a bulk material part, first a zinc layer is applied (applied) to the surface of the steel part by a galvanic deposition process, and then, in order to optimize the friction value of the steel part, a heat treatment is carried out at a temperature of 420 °C or lower for the targeted formation of an intermetallic zinc-iron phase in the galvanically deposited (vapor-deposited) zinc layer.

[0010] The inventors have recognized that the properties of the zinc-iron phase between the surface of the steel part and the galvanically applied (electrodeposited) zinc coating can be clearly controlled and adjusted by heat treatment. This makes it possible to increase the adhesion strength of the zinc layer in a simple and easily repeatable manner and to optimize the properties of the zinc layer, especially the hardness of the layer and the surface friction value. Furthermore, the heat treatment has the advantage that it can be carried out economically for any steel part, including bulk parts.

[0011] Furthermore, comparative tests have shown that, using the method according to the invention, a constant low friction value can be achieved in an easily reproducible manner without significant variation between individual steel components manufactured in accordance with the invention. Even when the steel components are used several times, especially when the screws are tightened several times, the friction value does not increase significantly and, ideally, remains essentially unchanged over at least 10 tightening processes, particularly preferably over at least 20 tightening processes. A low friction value is particularly preferred, although the absolute value of the friction value is of secondary importance initially.

[0012] The steel components are initially any components made from any ferrous alloy, preferably a ferrous carbon alloy, particularly preferably a ferrous carbon alloy with a carbon mass fraction of 2% or less. The individual steel components are preferably formed integrally (one-piece). Furthermore, the method is preferably used to coat a plurality of steel components simultaneously, and all the steel components coated simultaneously are particularly preferably formed identically to each other. In general, the plurality of steel components are preferably steel components each having at least one thread, particularly preferably steel components having exactly one thread. The steel components are preferably bulk components, particularly filigree bulk components, preferably connection means such as screws, clamp sleeves, pockets (containers, mesh bags), and / or electrical connection elements, or parts thereof, such as parts of a terminal block. Steel components for screw-clamp-sleeve connections are also preferred. The steel components can have any function, but the steel components are preferably provided for fixing conductors. The requirements imposed on the surface of the coated steel components, particularly the zinc layer and / or the passivation layer, are on the one hand good corrosion protection properties and on the other hand a constant coefficient of friction in repeated tightening.

[0013] For this purpose, a zinc coating is applied to at least a part of the surface of the steel part, preferably to the entire surface. According to the invention, this application is carried out by a galvanic deposition process, i.e. electroplating. Electroplating is understood to mean all methods of electrochemically depositing (precipitating) a metal on the metal surface of a steel part using an electrolyte (electrolyte solution), which is preferably a conductive liquid, in particular an aqueous salt solution.

[0014] Preferably, the pure zinc layer is applied by a galvanic deposition process, i.e. a pure zinc coating, and the pure zinc layer contains, in particular preferably, no more than 1% further metal atoms, except for metal atoms diffused from the surface of the steel part. On the other hand, other substances, in particular polymers from the deposition process, may be incorporated into the zinc layer. In particular, the zinc layer is applied by a pure and / or zinc electrolyte solution that does not contain iron and / or aluminium.

[0015] The galvanic application of the zinc layer can be carried out by heating the steel part and / or by means of an electroplating bath, or without adjusting the temperature. However, in general, the application is carried out without heating above 420 °C, preferably without heating above 100 °C, and particularly preferably without heating above 50 °C. Also, preferably, the steel part is not heated between electroplating and the heat treatment for forming an intermetallic zinc-iron phase.

[0016] The zinc coating is basically a complete zinc layer on the surface of the steel part. The zinc coating preferably completely covers the surface of the steel part and particularly preferably closes it completely so that oxygen and / or liquid cannot reach the surface of the steel part. The zinc coating with optimized friction has properties optimized with respect to the friction value or coefficient of friction, in particular a low friction value or coefficient of friction, and is understood to be a coating of zinc or a zinc alloy in which the friction value or coefficient of friction changes particularly little and / or has a particularly constant friction value or coefficient of friction during repeated tightening. In particular, at least the outer surface or rather the surface of the zinc layer is designed to obtain an optimized friction value or coefficient of friction.

[0017] The heat treatment may initially be in any form and, in particular, may have any temperature profile. Preferably, the heat treatment is carried out by heating to a constant temperature, holding at this temperature for a certain time, and subsequently cooling. Such a heating cycle can, in principle, also be repeated several times, but is preferably carried out only once. Furthermore, the heating is preferably carried out uniformly and / or without interruption to a specific temperature. Also, the cooling is preferably carried out continuously and particularly preferably lowered to the initial temperature before the heat treatment. Similarly, the heat treatment is carried out in air or in a gas atmosphere, i.e., outside the liquid. Particularly preferably, the heat treatment is carried out in a furnace, particularly in an electric furnace. For this purpose, the steel parts to be treated are preferably placed in the corresponding furnace. In particular, the heat treatment is annealing at a constant temperature. Particularly preferably, the heat treatment is carried out starting from a temperature of 100 °C or lower, very particularly preferably starting from a temperature of 50 °C or lower, and particularly preferably starting from room temperature.

[0018] According to the present invention, the heat treatment is carried out on the solid, i.e., at a temperature below the melting temperature of zinc of about 420 °C. Thereby, a diffusion process occurs within the solid, resulting in the formation, stabilization and / or further development of the desired intermetallic zinc-iron phase. Generally, regarding the temperature range of the heat treatment, it is preferably between 200 °C and 420 °C, particularly preferably between 230 °C and 420 °C, and very particularly preferably between 250 °C and 400 °C. The higher the temperature, the faster the formation, stabilization and / or further development of the desired intermetallic zinc-iron phase.

[0019] The formation of one or more different intermetallic zinc-iron phases according to the present invention also includes the stabilization and / or further development and / or modification of zinc-iron phases already formed during the galvanic deposition process. However, preferably, at least one intermetallic zinc-iron phase is formed by heat treatment, which was not previously present, or was present in very small amounts, or was present in very low proportions. Particularly preferably, the heat treatment serves to optimize the layer structure of the zinc coating, in particular the layer structure of the intermetallic zinc-iron phases contained therein. Very particularly preferably, the heat treatment is carried out to form several overlapping bonding layers and / or to stabilize and further develop these layers.

[0020] According to the present invention, at least one intermetallic zinc-iron phase is formed by heat treatment, where preferably a layer of pure zinc, i.e., the η-phase, is present simultaneously, in particular on the surface of the zinc coating, and the layer of pure zinc contains elements other than zinc only in the form of inevitable impurities and necessary auxiliary substances. In addition, further intermetallic zinc-iron phases are usually present in small proportions together with specific intermetallic zinc-iron phases formed by targeted methods.

[0021] Generally, depending on the heat treatment temperature and holding time, intermetallic zinc-iron phases with different stoichiometries are formed, and the stoichiometry directly affects the properties and especially the hardness of the deposited zinc layer, and thus directly affects the wear resistance and / or the friction value. There are a plurality of different intermetallic zinc-iron phases, but only some of them are decisive for the corrosion protection and friction value properties of the electroplated zinc coating on steel parts. First, for example, the face-centered cubic Γ phase, which is characterized by brittle material behavior, is formed on the zinc-plated steel part. Furthermore, a hexagonal δ phase with a low iron content may be formed, which is very ductile and is characterized by high corrosion resistance when occurring in a closed layer. The ζ phase with a monoclinic crystal structure is formed in the form of a brittle fence-like layer. The iron content of this compound is lower than that of the intermetallic compound phases already provided. Pure zinc (η phase) does not contain iron atoms and has the lowest hardness. However, the iron mass fraction in the intermetallic zinc-iron phase in the zinc coating of the steel part is preferably 10% or less, particularly preferably 7.5% or less, and very particularly preferably 6% or less.

[0022] Optimization of the friction value is understood to mean, in particular, a reduction in the initial friction value during the first operation or use of the steel part, and / or a reduction in the increase in the friction value during the subsequent operation or use of the steel part. Alternatively or additionally, optimization also includes keeping the friction value as low and / or constant as possible during repeated operation or use of the steel part. However, in particular, it is also optimal to reduce the friction value during repeated operation or use of the steel part.

[0023] In a preferred embodiment of the method for manufacturing a zinc coating with optimized friction according to the present invention, the application of the zinc layer and all subsequent method steps for manufacturing the zinc-coated steel part are carried out at a temperature of 420 °C or lower, whereby the melting of zinc, and thus undesirable phase transformations and the movement of undesirable materials on the surface of the steel part, can be easily avoided in an advantageous manner. Particularly preferably, the temperature does not exceed 400 °C.

[0024] According to a further advantageous development of the method according to the invention for producing a zinc coating having an optimized zinc coating, the holding time of the heat treatment is from 10 minutes to 10 hours, preferably from 20 minutes to 6 hours, particularly preferably from 30 minutes to 4 hours, whereby a good and extensive formation of the intermetallic zinc-iron phase is achieved. Here, the holding time is the duration of the heat treatment during which the zinc-coated steel part is held at an elevated temperature, in particular the maximum temperature of the heat treatment. Overall, the layer thickness and the iron content in the zinc layer can be controlled by varying the holding time and / or the temperature. As the holding time increases, the diffusion of iron into the zinc layer becomes stronger, and thus the iron content increases. Preferably, the heat treatment is carried out, particularly preferably, in a continuous furnace, especially when heat-treating a large number of steel parts, in particular bulk parts, simultaneously. However, alternatively, the heat treatment can also be carried out in a chamber furnace.

[0025] The duration of the heat treatment depends, inter alia, also on the number of steel parts being treated simultaneously. For example, when treating a particularly large number of parts simultaneously in a lattice box or crate (wooden frame), it is preferable for the duration of the heat treatment to be longer in order to ensure that the internal parts are also heated for a sufficient time. Thus, the heat treatment of individual steel parts or rather individually arranged steel parts can be carried out in a significantly shorter time. It also holds true that, with regard to the duration of the heat treatment, particularly in all steel parts heated simultaneously, the longer the duration, the better the reproducibility of the desired results.

[0026] Preferably, the minimum holding time is at least 15 minutes, particularly preferably 20 minutes, especially at a temperature of 300 °C, because at a temperature of 300 °C and a duration of 10 minutes, no measurable iron diffusion has yet been detected. The maximum holding time is not limited in principle, but since no significant change is observed even if the time increases significantly, a holding time of up to 4 hours is reasonable, particularly preferably, the holding time is 3 hours or less, and very particularly preferably, it is 2 hours or less. However, in principle, at low temperatures such as those between 220 °C and 330 °C, preferably between 230 °C and 320 °C, particularly preferably between 250 °C and 310 °C, a holding time of 3 hours or more, especially 4 hours or more, may be useful. Even with a holding time of 10 hours at 300 °C, a maximum iron mass content of 6% was measured in the zinc layer.

[0027] In order to clearly form, stabilize and / or further develop the iron-zinc ζ-phase (zeta phase), thereby enabling the achievement of a particularly good friction coefficient for zinc-coated steel parts, possible embodiments according to the invention provide that the heat treatment is carried out at a temperature between 220 °C and 330 °C, preferably between 230 °C and 320 °C, particularly preferably between 250 °C and 310 °C, very particularly preferably at 300 °C, and / or for a holding time between 30 minutes and 2 hours, particularly preferably between 45 minutes and 1.5 hours, very particularly preferably 1 hour. In this context, especially when the steel part is tightened several times, the ζ-phase has a great influence on the constancy of the friction value. Preferably, the heat treatment for forming, stabilizing and / or further developing the ζ-phase is carried out at a temperature of 300 °C for a holding time between 30 minutes and 2 hours, particularly preferably between 45 minutes and 1.5 hours, very particularly preferably 1 hour. At the same time, in addition to the ζ-phase, the formation, stabilization and / or further development of the iron-zinc δ-phase (delta phase) may occur, which may even be preferred in some cases.

[0028] However, the δ-phase is particularly ductile and provides particularly good corrosion protection for zinc-coated steel parts. Alternatively or additionally, it can also be specifically formed by heat treatment at a temperature between 310°C and 390°C, preferably between 330°C and 370°C, particularly preferably between 340°C and 360°C, and very particularly preferably at 350°C. In particular, a multi-step heat treatment that first forms, stabilizes, and / or further develops the ζ-phase and subsequently forms, stabilizes, and / or further develops the δ-phase at a high temperature is also conceivable. Alternatively, instead, the δ-phase can be formed first and then heat treatment can be carried out to form the ζ-phase.

[0029] Ideally, particularly at a temperature of 350°C, the holding time for forming, stabilizing, and / or further developing the δ-phase is longer than 30 minutes, more preferably longer than 45 minutes, most preferably longer than 1 hour, or, alternatively, between 1 hour and 3 hours, more preferably between 1.5 hours and 2.5 hours, and very particularly preferably 2 hours. In particular, when the temperature is low, it is also effective to increase the holding time.

[0030] In a preferred embodiment of the method according to the invention, the heat treatment is carried out at a temperature of 350°C or lower, preferably 340°C or lower, very particularly preferably at most 330°C, and / or at least 200°C, preferably at least 220°C, particularly preferably at least 230°C. Furthermore, the holding time is preferably 10 hours or less, particularly preferably 8 hours or less, very particularly preferably 5 hours or less, and / or at least 10 minutes, preferably at least 20 minutes, particularly preferably at least 30 minutes.

[0031] On the other hand, when the heat treatment is carried out at a fairly high temperature, particularly just below the melting point of zinc, the iron-zinc Γ phase (gamma phase) is thereby formed, stabilized, and / or further developed. Such heat treatment is preferably carried out at at least 390 °C, particularly preferably at at least 400 °C, very particularly preferably at at least 410 °C, and the maximum temperature is preferably 420 °C. This heat treatment is more preferably carried out over a long period of at least 3 hours, particularly preferably at least 4 hours, very particularly preferably at least 5 hours.

[0032] The surface of the steel part can be pretreated as necessary before applying the zinc layer. In this case, the pretreatment is particularly preferably carried out to condition the surface of the steel part. This includes, for example, cleaning of the surface, particularly degreasing. Polishing or chemical removal of the oxide layer is also conceivable. Furthermore, before applying the zinc layer, the surface of the steel part can also be pickled and / or pre-zinc plated. Pickling can be carried out by any method such as immersion pickling, spray pickling, rotary pickling, and / or electrochemical pickling.

[0033] In a preferred further development of the method according to the invention for producing a zinc coating with optimized friction on a steel part, a heat treatment is preferably carried out at a temperature between 200 °C and 250 °C to counteract (cancel out) possible hydrogen embrittlement before and / or after the zinc layer is applied to the surface of the steel part in a galvanic deposition process and / or after pre-zinc plating. In particular, this heat treatment is an aging for hydrogen embrittlement, by which hydrogen diffuses from the steel part and / or becomes more uniformly distributed within the material, thereby being able to at least significantly reduce or completely avoid or eliminate hydrogen embrittlement. Also, it is preferable to carry out the final zinc plating in the galvanic deposition process immediately after this heat treatment, particularly immediately after aging. Such heat treatment, particularly aging treatment, is particularly useful for significantly strengthened steel base materials of steel parts.

[0034] For even better corrosion protection, in particular for protecting the zinc layer from abrasion, protecting the pure zinc on the surface of zinc-coated steel parts from oxidation, and further achieving an even better optimization of the coefficient of friction, the zinc surface is preferably adjusted in a galvanic deposition process, in particular by passivation of the zinc surface, after the zinc layer has been applied to the surface of the steel part. The passivation is preferably effected by an organic ceramic coating or by at least one, preferably several, organic ceramic layers. The passivation is preferably carried out by immersion in a passivating agent. Furthermore, the organic ceramic layer is preferably formed mainly from chromium and / or zinc oxide.

[0035] According to a preferred embodiment of the method for producing a zinc coating with optimized friction according to the invention, a heat treatment for forming a zinc-iron phase is provided to be carried out after or rather following the passivation when a heat-resistant passivation layer is used. For this purpose, the passivation layer must be heat-resistant up to at least the maximum temperature of the heat treatment, preferably at least 10 °C, particularly preferably at least 20 °C higher than the maximum temperature of the heat treatment. In particular, the heat treatment for forming the zinc-iron phase is preferably carried out as the last manufacturing step of the zinc-coated steel part. Also, preferably, the passivation is carried out immediately after the zinc layer has been applied to the surface of the steel part in a galvanic deposition process in order to protect the newly formed zinc layer from oxidation as soon as possible. In the case of a non-heat-resistant passivation layer, a corresponding heat treatment must be carried out before the passivation.

[0036] According to a further preferred development of the method according to the invention for producing a zinc coating with optimized friction, the zinc layer is preferably applied to the surface of a steel part in a galvanic deposition process using a polymer containing nitrogen and / or an alkaline zinc electrolyte preferably free of cyanide. The choice of the zinc electrolyte used in the galvanic deposition process also affects the friction value of the zinc-coated steel part, which is due in particular to the substances incorporated in the zinc layer, especially organic substances. Weakly acidic electrolytes and / or electrolytes containing sulfur-containing surfactants have been found to be suitable only to a very limited extent, since a significant increase in the friction value was observed. Therefore, the pH of the zinc electrolyte is preferably greater than 2.5, particularly preferably greater than 5.0, very particularly preferably greater than 7.0, and especially preferably greater than 8.0.

[0037] Subsequently, several embodiments of the invention will be described in more detail with reference to the drawings.

Brief Description of the Drawings

[0038]

Figure 1

Embodiments for Carrying Out the Invention

[0039] In a first embodiment of the method for producing a zinc coating with optimized friction on a steel part, a pure zinc coating is first applied to the surface of a steel screw for an electrical terminal block by a galvanic deposition process. An alkaline zinc electrolyte free of cyanide is used in an aqueous solution, and the solution preferably contains a nitrogen-containing polymer. Using this alkaline zinc electrolyte, the nitrogen-containing polymer is at least partially incorporated into the zinc coating, as a result of which the friction value of the steel screw is significantly stabilized.

[0040] Immediately after coating, a heat treatment is performed in which the zinc-coated steel screw is heated in a furnace to 300 °C for 30 minutes to form and stabilize the ζ zinc-iron phase between the pure zinc on the surface of the coated steel screw and the steel surface. This optimized layer structure is, in this case, characterized by the stabilization of the ζ phase in the transition (migration) region from the zinc layer to the substrate. The course of the friction value is characterized by a substantially constant friction value over 10 tightening cycles, and as a result, the variation in the friction coefficient can also be significantly reduced.

[0041] Alternatively, the duration of the heat treatment can be between 20 minutes and 4 hours. In either case, one temperature cycle consists of one heating, holding at 300 °C, and cooling. Such a heat treatment for forming the intermetallic zinc-iron phase can be carried out, for example, in a continuous furnace, where the steel screw is heated to 300 °C at a heating rate of about 10 K / min and held at this temperature for 30 minutes. Subsequently, it is cooled in still air, especially at a cooling rate of about 5 K / s. However, furthermore, heat treatment at a lower temperature for a longer time is solely possible. For this purpose, for example, the steel screw is heated in a chamber furnace to 250 °C at a heating rate of about 10 K / min to form the intermetallic zinc-iron phase, and held at this temperature for about 6 to 10 hours or longer. Subsequently, it is cooled in still air, especially at a cooling rate of about 5 K / s.

[0042] Particularly preferably, after the heat treatment at 300 °C, complete cooling is not performed. As shown in FIG. 1, the steel part is held at a temperature of 250 °C for a long time, especially for 6 hours. Thereby, more uniform results are obtained for all steel parts, and the layer structure of each steel part is less disrupted and more uniform.

[0043] In another embodiment, the electroplating of the steel part of the electrical contact element is carried out using a cyanide-free alkaline zinc electrolyte. Passivation is carried out immediately thereafter, and an organic ceramic layer mainly formed from chromium and / or zinc oxide is applied to the zinc-plated surface of the steel part.

[0044] Subsequently, as the final manufacturing step of the steel component, heat treatment of the zinc-coated and passivated component is performed in a furnace at a temperature of 300 °C for 30 minutes.

[0045] Another embodiment starts with a component similarly coated with zinc, and the heat treatment is carried out in two steps. First, the component is heated to 350 °C and held there for 30 minutes. Then, the component is cooled to 300 °C and held there for an additional hour.

[0046] After being completely cooled, passivation is performed using a non-heat-resistant passivating agent.

Claims

1. A method for producing a zinc coating with optimized friction due to a stable low friction value or coefficient of friction on a steel part having at least one thread for fixing an electrical conductor to an electrical connection element, comprising: applying a zinc layer to the surface of the steel part by a galvanic deposition process, and then heat-treating at a temperature of 420 °C or lower to form an intermetallic zinc-iron phase within the galvanically deposited zinc layer, wherein at least one intermetallic zinc-iron phase is formed by heat-treatment at a temperature of 250 °C for 6 to 10 hours on the surface of the zinc layer so as to obtain a constant friction value or coefficient of friction when the thread is repeatedly tightened. A method characterized by the above.

2. A method for producing a zinc coating with optimized friction on a steel part according to Claim 1, wherein the application of the zinc layer and all subsequent method steps for manufacturing the zinc-coated steel part are carried out at a temperature of 420 °C or lower. A method characterized by the above.

3. A method for producing a zinc coating with optimized friction on a steel part according to Claim 1 or 2, wherein the surface of the steel part is pickled and / or pre-zinc plated before the zinc layer is applied. A method characterized by the above.

4. A method for producing a zinc coating with optimized friction on a steel part according to any one of Claims 1 to 3, wherein before the zinc layer is applied and / or after pickling and / or after pre-zinc plating, further heat-treatment is carried out at a temperature of 200 °C to 250 °C to counteract possible hydrogen embrittlement. A method characterized by the above.

5. A method for producing a zinc coating with optimized friction on a steel part according to any one of Claims 1 to 4, wherein the zinc layer is applied to the surface of the steel part in a galvanic deposition process using an alkaline zinc electrolyte containing a nitrogen-containing polymer. A method characterized by the above.

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