JPS609100B2 - Pretreatment method for metal surfaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pretreating metal surfaces of flat or profile materials under vacuum for subsequent vacuum deposition steps.

This method is particularly preferably used to obtain a mechanically tight, non-porous deposited layer on the steel strip in a vacuum deposition system. Metal substrates, especially steel strips, are cleaned in air before being introduced into the vacuum deposition apparatus.

The Motomura surface is cleaned of fats, oils, emulsions, etc. by cleaning caustic solution and/or by electrical methods. However, these cleaning methods are still unsatisfactory in order to obtain a deposited layer that is mechanically tightly bonded. Therefore, prior to vapor deposition, the metal substrate is subjected to further pretreatment. In this case, it is necessary to achieve the desorption of a layer of volatile foreign substances such as water or adsorbed gases, as well as the activation as high as possible of the atomic layer near the surface of the substrate lattice. It is known to pretreat surfaces mechanically in air.

This pretreatment is carried out by means of a rotating brush (US Pat. No. 3,123,493). In this case, the surface dirt is certainly sufficiently removed, but the desorption and surface activation required to obtain a tightly adhered deposited layer is not achieved. This is because the surface is rendered unusable for subsequent vacuum deposition due to the physically adsorbed gas coating and the chemically adsorbed gas coating again immediately after treatment due to atmospheric influences, and a tightly bonded layer is obtained. That's because there isn't. Furthermore, it is known to carry out pre-brushing under vacuum, especially when depositing zinc on steel strips.

(German Patent No. 1932812). in this case,
The teaching is to hold the ferrous substrate after zinc deposition at a temperature between 232o0 and the alloying (iron/zinc) temperature as well as the temperature at which the zinc evaporates from the ferrous substrate. Brushing is carried out under a gas pressure of less than 10-2 Pascals. The time between mechanical pretreatment and vapor deposition treatment is up to 3
It needs to be calm sand. Brushing under reduced pressure as a mechanical pretreatment results in a clean adsorbent surface in the case of sufficiently high working densities, in which case the associated deformation of the substrate in the near-surface region leads to Causes lattice defects. The totality of these effects results in a mechanically active state of the surface. In order to later obtain a tightly adhered deposited layer,
The steel strip temperature required for this brushing process is too high, the pressure in the vessel is too low and the time between brushing and deposition is too short, resulting in economic problems and back evaporation. fundamental technical difficulties arise. It is also known to separate the vacuum brushing step from the vapor deposition step (GDR 138 785).

This method has the disadvantage that the equipment outlay is relatively high and that the time between the brushing step and the coating step must be less than one ash. The object of the invention is, besides avoiding the disadvantages of the prior art, to provide a method which is suitable for large-scale industry with low energy consumption and which allows for the advantageous pretreatment of large cross-sectional areas and even wide strips. It is to create.

The object of the invention is to find a method for pretreating metal surfaces under vacuum for subsequent processing in air or under vacuum.

In the subsequent vacuum deposition step, a mechanically tight, non-porous deposited layer is formed using low pretreatment temperatures (near room temperature), high pressures and long times between pretreatment and deposition (in the range of several minutes). (within) should be economically obtainable. Post-treatment in the atmosphere, for example painting, is possible even after a long period of time - without the pre-treated material corroding during that time. This method should be suitable for each cross section and thickness of rods and strips.

Furthermore, the method should also be suitable for many material combinations. This problem is solved in particular by combining a one-stage or multi-stage brushing process with material ablation of 0.5 to 21 m and a vapor deposition process.

The vapor deposition step is combined with the only or last brushing step such that the deposited material reaches the surface during the brushing step and is partially mechanically incorporated. This causes the surface to be desorbed, activated and budded.
Experiments have shown that the lower limit of the amount of abrasion by brushing is 0.5 wm, which is the minimum value that provides sufficient mechanical activation required for sufficient adhesion strength of the deposited layer.

Further, if the amount of scraping is more than 2 m, there will be a problem in removing scraps and the base material will be scraped unnecessarily. The material deposited during the brushing step may be the same as in the subsequent vacuum deposition step, or may be different.

The brushing step is advantageously carried out in a pressure range of 10-2 to 1 pipascal.

This pressure range is a value constrained and determined by the vacuum conditions of the coating process, since the entire process is carried out in a vacuum evaporator. Another advantageous embodiment of the invention is designed such that the temperature of the surface to be treated is between 20 and 8000 °C during the deposition process.

This temperature range is determined in relation to the compensation heat, especially in the case of thin layers, in order to avoid back-evaporation at higher temperatures. It has been found to be advantageous for the surface and the bristles of the rotating brush to have relative movements in opposite directions. The deposition in the brushing process is carried out either by means of a special evaporator in the last brushing stage or by atomization in the section of the last brushing stage in the actual deposition chamber.

This combined brushing/dusting process is carried out in such a way that, by brushing, such a mechanical working of the surface is carried out and that this intimate working of the surface achieves sufficient desorption and activation.

Due to the vapor deposition during brushing, the evaporated particulates reach the brush or the surface before brushing and mechanically coalesce on the surface in a thickness of one to several atomic layers. Mechanical processing of the surface by a rotating brush creates an energetically favorable state of high lattice vacancy concentration near the surface, so that the coalescing metal vapor atoms have favorable conditions for adsorption or coalescence onto the surface. This is a prerequisite.

The adhesion of the layer is surprisingly independent of its temperature, for example in the case of iron, and also independent of the melting temperature of the layer metal. This is because the bonding strength of the zinc layer, aluminum layer and copper layer is uniform and very good. Thermally limited bonding methods, such as those often required in bonding metals together, are clearly of little or no use in the case of surfaces that have been mechanically worked by brushing. The short-term corrosion resistance is up to two orders of magnitude longer when zinc is incorporated in multiple atomic layers by the method of the invention compared to untreated steel strips. On the basis of this confirmed short-term corrosion effect, the method is suitable for workpiece materials susceptible to corrosion, especially iron and iron alloys, which are not exposed to high corrosive attack, and the subsequent vapor deposition process is free from corrosion or other Subsequent protection can be provided by anti-corrosion methods, such as paint applications or plastic coatings. The effectiveness of combining brushing and deposition into a single process is amazing.

Brushing alone produces a metal-selective surface, which, as is known, is corroded by physical and chemical adsorption even after very short periods of use in the atmosphere.
If the probability of adhesion of gas particles is high even under the low pressure of a vacuum state, the surface will be covered again with 1 patomic layer of gas particles after 1 second in the range of 1 Pascal. However, it is certainly observed that the samples brushed and deposited in this way have a much higher corrosion resistance than the samples that are only brushed. This combination clearly provides, on the one hand, corrosion inhibition and, on the other hand, good conditions leading to a well-adhered deposited layer. EXAMPLE An important field of application of the invention is the pretreatment of steel strips for a subsequent vacuum deposition step with zinc.

This will be explained in detail below. A brush system consisting of a number of brushes is placed in a container prepared for pretreatment under vacuum.

Claims (1)

[Scope of Claims] 1. The material to be treated is mechanically brushed in one or more stages to a thickness of 0.5 to 2 μm.
1 on the material to be treated to remove and deposit the material in the last or only step of the brushing process.
A method for pretreating metal surfaces under vacuum for a subsequent vacuum deposition step, characterized by brushing and simultaneous evaporative deposition of layers up to several atomic layers thick. 2. A method according to claim 1, wherein the material deposited during the brushing step in the case of post-treatment by vapor deposition is the same material or another material. 3. The method according to claim 1 or 2, wherein the brushing step is carried out under a pressure of 10^-^2 to 10^2 Pascals. 4 The temperature of the surface of the material to be treated up to the point of vapor deposition is
4. The method according to any one of claims 1 to 3, wherein the temperature is selected from -80<0>C.