EP1606436B1 - Device and the parts thereof for producing electrodeposited dental shaped pieces - Google Patents

Abstract

The invention relates to an apparatus for electrodeposition, in particular for the electrodeposition of shaped dental parts. In addition to the standard components, this apparatus includes at least one magnetic connecting means for producing the electrical contact for the electrodeposition between at least one electrode and the current/voltage source of the apparatus. Furthermore, the invention describes an electrode which serves as a holding/contact element and has a magnet, and a component which interacts with this electrode and has a second magnet for providing the magnet contact-connection. This component is then assigned to the current/voltage source or a head or cover part of an electrodeposition appliance.

Description

The invention relates to a device and an electrode for the electrodeposition, in particular for the electrodeposition of dental moldings such as frameworks for crowns, inlays, bridges and the like.

The galvanic deposition, d. H. the deposition under current flow, metallic layers has been known for a long time. If moldings are formed, that is, stable bodies in themselves, this is called electroforming.

The use of galvanoforming in dental technology dates back to the early 1960s, when Rogers and Armstrong inlays and onlays produced electroplated. The then still cyanidic gold baths are still different, not cyanidic gold baths, such as. B. the sulphite gold bath of the applicant ( EP 0 360 848 ).

Galvanically deposited gold layers have a much higher hardness than cast ones, which is between 60-80 HV or between 100-130 HV, depending on the electrolyte composition. These electroplated gold layers are generally free of voids, inhomogeneities and impurities that are unavoidable during casting. Nevertheless, it may be due to improper work and thereby introduced impurities or due to manufacturer-specific device-related process fluctuations to separation problems. These show up z. By plating impurities, bud formation, layering or holes in the layer. Such disturbances can in the worst case lead to the loss of burning stability and thus render the resulting layers / shaped bodies unsuitable for further dental processing. The problem in the production of dental prostheses / dental moldings by electroplating lies in the sometimes complicated geometric shapes and the special precipitation properties that are needed. For reasons of stability and processing, in this case a uniformly homogeneous layer structure and a coating thickness distribution which is as uniform as possible are desirable. The current-controlled galvanic deposits, as z. B. arise in the AGC ^® devices of the Applicant, are much more reliable process and deliver reproducible good properties.

For several years, various devices have been commercially available in the dental market, which are used in dental laboratories for the galvanic production of dental prostheses or scaffolding. Scaffolds are understood to mean the metallic basic constructions such as crown copings or bridgehead coping, which later are veneered with ceramic by the dental technician, for example, and then fired to the final denture. These scaffolds are made of fine gold for a variety of reasons, especially the biocompatibility of the patient. The devices mentioned are so-called Kleingalvanisiergeräte, which, in contrast to industrial electroplating plants do not work continuously, but discontinuously. The process times are - depending on the type and size of the device - usually a few hours, for example 1 to 16 hours. These devices can usually be placed and operated on a simple workbench, usually with a usable volume of electrolyte about a liter or less, and a capacity of a few dental prostheses, e.g. B. Kronenkäppchen that can be produced therein in a process.

The users of such electroplating equipment are usually employees in a dental laboratory, for example, dental technicians - ie not specially trained personnel for electroplating. Therefore, it is important that such electroplating equipment be easy and safe to operate, in terms of the quality of the dental prostheses produced therein as well as the health of the operator. Therefore, manufacturers of such electroplating equipment strive to offer equipment with the greatest possible user-friendliness and process reliability. As examples are here to the AGC call ^® -Gerätepalette the Applicant, which covers for example capacities 1-16 simultaneously electroplatable objects and process times of from 1 to 16 hours.

In connection with maximum user-friendliness and process reliability, the contacting is also to be seen. In the galvanic element "Galvanisiergerät" is an electrolyte (eg. As the AGC ^® gold bath of the applicant), an anode, and (at least) one provided with a conductive silver duplicate model of a tooth or the oral situation, which is connected as the cathode. The duplicate model is connected to the current / voltage source in the device via a holding rod / wire, which usually acts as an electrical contact at the same time. This support rod may be a stainless steel rod or, for example, a copper / titanium rod, and may be simple or reusable. In this type of contact bars, since some part is always immersed in the electrolyte during the process, it should be electrically insulated from the electrolyte so that it will not be gold plated. This is usually done by a so-called shrink tubing made of plastic or appropriate coatings.

The contact rods / support rods are then connected via a plug contact (eg a socket), through a metallic collet or a crimp contact with the current / voltage source in the device. It is also important for contact with the device that it has a long life and, if it is inside the galvanizing cell, that it is not susceptible to corrosion. Corrosion products can contaminate the electrolyte and endanger the entire function of the process. The preparation of the contact, so the equipment of the device with duplicate models and the electrical contact is made by the operator.

Here, special demands are placed on the contacting method, on the one hand to ensure process reliability and, on the other hand, to keep handling as simple as possible. For process reliability, it is z. B. indispensable that the electrical contact permanently, so over the entire process time, remains reproducibly good.

Disadvantage of the mentioned types of contacts is that always contact resistances occur that may be undefined and may prevent a sufficient flow of current to the duplicate model to be plated. In such cases, a failure in the galvanization occur, which manifests itself in that the galvanized gold framework is too thin and / or disturbed by the layer structure ago or that in extreme cases, the galvanization process is completely prevented. In addition, the above-mentioned contacts are sometimes difficult for the operator to handle and the parts connected to each other difficult to adjust to each other.

In the FR-A-1226638 a device is disclosed in which an insert of magnetic supports for the electrolysis is provided. There, however, there is a direct galvanic coating of the existing rod-like electrodes themselves.

In the EP-A-0690151 a special electrode for hard chrome plating is shown, which consists essentially of an electrically conductive, hollow component carrier, which is provided for contacting a plurality of components to be coated. Inside the component carrier is provided over the entire length of the carrier extending dust-shaped magnet.

The invention therefore has the task of avoiding the problems encountered in the prior art in the contacting or at least largely rule out. The parts to be electroplated or

Models should be easily connectable to the power / voltage source, and this connection should be reliably maintained throughout the process time. Furthermore, the electrical contact should also be able to be interrupted again in a simple manner in order to be able to introduce new parts / models into the electroplating apparatus.

This object is achieved by the device having the features of claim 1 and by the electrode having the features of claim 8. Preferred embodiments of this device or the electrode are shown in the dependent claims 2 to 7, and 9 to 13, respectively. The wording of all claims is hereby incorporated by reference into the content of this specification.

The device according to the invention has at least one current / voltage source and electrodes which can be arranged in a vessel which can be filled with an electrolyte. At least one magnetic connection means is provided between at least one electrode and the current / voltage source for producing the electrical contact for the electrodeposition. The essence of the invention is based on the fact that a magnetic contact for the preparation of the electrical contact between the electrode and the current / voltage source is provided. The magnetic adhesive force of two standing under electrical voltage magnetic metal parts causes, that an electric circuit is closed by the corresponding contact of these parts.

From the previous statements it follows that the inventively provided magnetic connecting means is formed in two parts. In this case, such a two-part design of a Magnet as the first part and a second part made of a magnetizable metal. In a particularly preferred embodiment, the two-part magnetic connection means consists of two magnets which establish the necessary contact by their attraction. When using two magnets, a particularly good holding force and minimal contact resistance are achieved.

The magnets mentioned are preferably so-called permanent magnets or permanent magnets, as known from the prior art. These provide the required holding force on the magnetizable metal or on each other without the use of other tools. Furthermore, the magnets used preferably have a circular cross-section. Such magnets can be referred to as round magnets.

In the device according to the invention, a magnet is assigned to the current / voltage source. If the invention is realized in conjunction with the electroplating devices mentioned above, such devices often have a so-called head or cover part, which is arranged when carrying out the electrodeposition over the vessel which receives the electrolyte. In such embodiments, the magnet associated with the current / voltage source is preferably arranged on this head or cover part. In this way, the contact with the electrodes can then be produced particularly easily. In the mentioned embodiments, in particular at the current / voltage source, preferably at the head or cover part, there is a sleeve which receives the magnet. Such a particularly preferred embodiment will be explained later in connection with the drawing.

In the device according to the invention, a magnet is assigned to the electrode or a part of the electrode. As explained above, acts it is expediently in the electrodes to rod-like components, which can be referred to as contact bars / support rods. Accordingly, in the latter embodiments, the magnet is preferably attached to these rod-shaped components. Such electrodes, in particular rods, then preferably have a sleeve-like receptacle into which the magnet is inserted. This too will be explained in more detail in connection with the drawing.

• das Ende der stabförmigen Elektrode ohne magnetisches Verbindungsmittel zur Verbindung mit mindestens einem zu beschichtenden Teil oder Modell vorgesehen ist, und
• die Elektrode an ihren Außenflächen mit einer elektrisch nicht leitfähigen Beschichtung versehen ist, wobei die für den Kontakt mit der Strom-/Spannungsquelle vorgesehene Fläche und das Ende der Elektrode ohne magnetisches Verbindungsmittel frei von einer solchen Beschichtung sind.

Finally, the device according to the invention comprises the features that

• the end of the rod-shaped electrode without magnetic connection means is provided for connection to at least one part or model to be coated, and
• the electrode is provided on its outer surfaces with an electrically non-conductive coating, wherein the area provided for the contact with the current / voltage source and the end of the electrode without magnetic connecting means are free of such a coating.

As is apparent from the previous description, the invention also includes a new electrode for the electrodeposition of dental moldings. This electrode according to the invention is designed so that it has at least one magnetic connection means, in particular at least part of a two-part magnetic connection means. This electrode has the shape of a rod, as it basically corresponds to the shape of the previously known contact bars / support rods.

According to the invention, in the case of the new electrode, the magnetic connection means or its part is provided at one end of the electrode. This is usually the end that is associated with the galvanic deposition after making the electrical contact of the current / voltage source.

The magnetic connection means may be a magnetizable metal, which then interacts with a magnet which is associated with the current / voltage source. Preferably, however, the magnetic connection means on the electrode is a magnet as already described above. Such a magnet is preferably a permanent or permanent magnet. Magnets with a round cross section (round magnets) are preferred.

In further preferred embodiments of the electrode according to the invention, the magnet is in a sleeve-like receptacle at one end of the (preferably rod-like) electrode. To protect the magnet in this recording from corrosion, this recording is preferably closed with a lid part. This cover part is preferably flat. In this case, the upper side of the cover forms the contact surface which cooperates with the other part of the magnetic connection means assigned to the current / voltage source.

The electrode itself can basically be constructed of any conductive material. However, it is preferred if the electrode and also an optional cover part for closing the receptacle receiving the magnet is made of stainless steel. This material offers good protection against corrosion. If appropriate, the entire outer surface of the electrode, or preferably at least the upper surface of the cover part forming the contact surface, may be coated with another metal. Such a metal coating may serve to further increase corrosion resistance or electrical conductivity. Emphasizing here are coatings of gold or gold alloys, which can preferably be deposited galvanically on the electrode or only on the cover part.

The electrode according to the invention preferably has a smaller cross-section at its "lower" end, which carries the parts / models to be coated during the electrodeposition, than at its "upper" end facing the current / voltage source or the head or cover part. Preferably, the electrode tapers at its "lower" end or runs there pointedly. In this way, the parts / models to be coated easier to attach to the same time serving as a holding electrode electrode.

Further, the electrode according to the invention is characterized in that it is provided on its outer surfaces with an electrically non-conductive coating, wherein the intended for contact with the current / voltage source surface and the end of the electrode without magnetic connection means are free of such a coating.

The coating may in particular be a plastic coating.

The coating, in particular plastic coating, prevents galvanic deposition of metal there and / or that the electrode is attacked by corrosion and damaged.

The device according to the invention or the electrode according to the invention have a whole series of advantages over those with the previously known contacts.

Thus, in the invention, the required electrical contact is made by a directional magnetic force. This is strong enough to maintain this contact throughout the galvanic deposition process. If the aforementioned embodiments with two cooperating parts of the magnetic connection means, in particular the two magnets mentioned, used, this advantage is particularly evident. By the directed magnetic force, the two cooperating parts are inevitably pulled into the correct position to each other, so that the two parts, in particular the two magnets, opaque one above the other. In this way it is ensured that there is always a defined contact surface and a bad Galvanisierergebnis by undefined high contact resistance is virtually eliminated.

A further advantage of the invention is that the electrical contact can be made quickly and easily by the operator. Thus, the electrode / the contact bar is easily replaceable, which significantly increases the working efficiency for the operator. In addition, no maintenance of the components is necessary because, for example, contamination of the contact surfaces is largely excluded. Should a cleaning be necessary, it can be done simply by wiping.

Yet another advantage of the embodiments according to the invention is shown by taking into account the process temperatures of conventional galvanic deposits, in particular in the dental field. Such process temperatures are usually in the range between 50 ° C and 70 ° C, usually at about 65 ° C. This has the consequence that condensation products usually collect from the electrolyte in the upper part of the vessel or the galvanizing cell. Due to their chemical composition, such condensation products can lead to corrosion of the parts which make the electrical contact. The products resulting from the corrosion can then in turn enter the electrolyte and contaminate it. Such impurities can then be co-deposited, for example, together with the gold, and thus greatly deteriorate the quality of the electrodeposited molded parts, in particular the denture scaffolds. By contacting the invention caused by this can be almost certainly excluded. This relates in particular to the embodiments in which the magnets are located in a sleeve-like component, which is securely closed with a cover part.

Especially in the latter embodiments with a kind of jacket construction for the magnets used to make the electrical contact, the advantages according to the invention are particularly apparent. In such embodiments, the magnet is completely protected by this jacket construction. Accordingly, a corrosion-resistant stainless steel is preferably used as the material for such constructions. Corrosion of the electrical contact is therefore excluded. Bringing on the stainless steel electrode / stainless steel rod, at least on the contact surfaces such as the lid part, in addition to a gold layer, this corrosion resistance is on the one hand further increased, and on the other hand, an excellent electrical conductivity is achieved. This, together with the other design features, becomes an outstanding permanent and reproducible good electrical transition at the contact points between electrode / support rod and power / voltage source or head or cover part created.

Finally, the electrode according to the invention or the holding / contact rod according to the invention is permanently reusable. This is especially true because it additionally on its surface with a protective layer, preferably a non-conductive protective layer such. B. a plastic coated.

These and other features of the invention will become apparent from the examples and drawings described below taken in conjunction with the claims. The individual features can be realized alone or in combination with each other.

Fig. 1

eine schematische Querschnittsdarstellung einer erfindungsge- mäßen Elektrode bzw. eines erfindungsgemäßen Halte-/Kontakt- stabs mit eingesetztem Magneten, und

Fig. 2

eine schematische Schnittansicht eines erfindungsgemäßen Bau- teils mit eingesetztem Magneten, das einer Strom-/Spannungs- quelle bzw. einem Kopf- oder Deckelteil einer erfindungsgemäßen Vorrichtung zugeordnet werden kann.

In the drawings show:

Fig. 1

a schematic cross-sectional view of an inventive electrode or a holding / contact rod according to the invention with inserted magnet, and

Fig. 2

a schematic sectional view of a component according to the invention with inserted magnet, which can be assigned to a current / voltage source or a head or cover part of a device according to the invention.

Examples

An applicator of the type AGC ^® Speed is modified according to the invention. It is assumed that the unicellular version of this device, which is not shown in detail in the figures. The device essentially consists of a housing that contains the current / voltage source and picks up the control. In addition, the device has an electrolyte container with a head or lid part, to which the anode and the cathode, which is provided with the part to be coated / model to be attached. With the ^AGC® Speed device of the applicant, the complete electrolyte container with head or cover part can be removed from the device. This simplifies the introduction of the parts / models to be coated in the electrolyte container and protects the other components of the device from contamination, for example by the electrolyte.

In the previous embodiment of the AGC apparatus of the Applicant ^® speed plug contacts were used for the fixing / bonding the formed usually as a ring anode and anode in particular connected as cathode holding / contact rod. The rod-shaped upper ends of these electrodes were inserted into corresponding receptacles in the head or cover part and latched, for example. However, this reliable working contact often did not allow quick replacement. In addition, the contact surfaces had to be protected relatively expensive against corrosion by rising from the electrolyte vapors.

For the inventive modification of the Applicant's described device, the two come in the Figures 1 and 2 shown components used.

FIG. 1 shows an electrode 1 according to the invention in the manner of a holding or contact rod. This electrode 1 is made of stainless steel and has at its one end 2 a smaller cross-sectional area than at its other end 3. The end 2 is formed in the manner of a tip, which for fixing the electrode to an in FIG. 1 not shown part or model is used, which is to be electroplated. This will be explained in more detail below.

At the other end 3, a sleeve-like receptacle / recess 4 is provided, in which a magnet 5 is introduced. This magnet 5 is a permanent magnet with a round cross-sectional area, i. H. a so-called round magnet. To protect these magnets 5 against corrosion, a cover part 6 is provided on the electrode 1, which is also made of stainless steel and the receptacle 4 seals. By the construction of the end 3 of the electrode 1, the magnet 5 is thus fully encased.

According to the invention, the surface 7 present on the outside of the cover part 6 forms the contact surface, via which the magnet 5 can cooperate as a part of the two-part magnetic connection means with a second part. In order to optimize the electrical contact produced via the magnetic force, the surface 7 or possibly also the entire outer surface of the electrode 1 may be gold-plated. This is in FIG. 1 not shown in detail. Likewise, the outer surfaces of the electrode 1, except for the surface 7 serving as the contact surface, may be provided with a plastic coating. This then prevents that takes place on the electrode itself unwanted galvanic deposition. If the plastic coating is not present, this deposition is prevented by the operator by other measures, for example by wrapping the electrode 1 with a shrink tube.

FIG. 2 shows a sleeve-like member 11 with a round cross section, which is also made of stainless steel. This component 11 is the counterpart of serving as a holding / contact rod electrode 1 from FIG. 1 . The component 11 may be introduced, for example in the above-explained head or cover part of the AGC ^® speed device of the applicant or be otherwise associated with the current / voltage source, in another construction of a Galvanisiergeräts.

The component 11 has at its one end 12 a receptacle / recess 13, in which a magnet 14 is introduced. Again, the magnet 14 is a permanent magnet with a round cross-section, d. H. a round magnet. The receptacle 13 with the round magnet 14 is sealed with a lid part 15, which is also made of stainless steel. In this way, it is also prevented here that the magnet 14 is corroded by rising vapors from the electrolyte.

The existing on the cover part 15 outer surface 16 is in the component 11, the contact surface for the interaction of the magnet 14 with the other part of the two-part magnetic connection means. Again, the surface 16 and optionally the entire outer surface of the component 11 may be gold plated. Corresponding plastic coatings (with the exception of the surface 16) are also possible.

If one then moves the surface 7 of the electrode 1 in the direction of the surface 16 of the component 11 (with the orientation of the magnets 5 and 14 inserted correctly), these two surfaces are attracted by the magnetic force and positioned correctly relative to one another. At the same time the necessary for the electrodeposition electrical contact is made. The electric current can then flow, for example, via the component 11 with the surface 16 into the surface 7 of the electrode 1 and thus also to a model of a tooth replacement part fastened to its end 2. In the same way, an electrical contact can of course also be made in an anode connected as an electrode. Such an anode will usually just be a metal rod.

With an AGC ^® Speed device of the applicant, with the components according to the Figures 1 and 2 modified tooth replacement parts are produced by electroforming. In this case, the component 11 (see FIG. 2 ) is introduced into the head or lid part of the device, and the electrode 1 (see FIG. 1 ) is used as a holding / contact rod for the tooth replacement part or the model.

The two experiments presented below assume, firstly, a plaster stump which is rendered conductive with conductive silver in a customary manner. On the other hand, it is assumed that a metallic primary crown, which is also coated with conductive silver to account for the cement, which later primary crown connects with secondary crown (double crown technique). The electrolyte used is a sulfite gold bath of the applicant. However, the composition of the bath is not critical to the occurrence of the advantages of the invention.

The preparation and the performance of the electrodeposition is summarized in the following table. In both examples, perfect moldings are obtained from fine gold with layer thicknesses of 300 microns. This shows that the "magnetic contacting" according to the invention leads to the high quality parts required in dental technology. Taking into account the existing in comparison to the previous contacts benefits, as they were already mentioned in the introduction, so the modification of the device according to the invention represents a real progress. example 1 2 Die material kind Plaster die; Repair kit Metallic primary crown; Repair kit Magnetkontaktierung Contact in the device Magnet in stainless steel sleeve Magnet in stainless steel sleeve; gilded Contact staff Magnetic contact rod, E-steel sleeve; shrinkable tubing Magnetic contact rod, stainless steel sleeve; gold plated; shrinkable tubing Electric contact Magnet / stainless steel / stainless steel / magnet Magnet / stainless steel / gold / gold / stainless steel / magnet Galvanisierparameter Time 1.5 h 4h Average current density 2.5 A / dm ² 2 A / dm ² current form pulse current pulse current temperature 65 ° C 65 ° C Galvanisiergerät kind AGC Speed AGC Speed description In the plaster die a 1.2 mm thick hole is drilled and glued the magnetic contact rod with its thin uninsulated side with superglue. The surface to be plated is coated with conductive silver and a connection drawn from the surface to the rod. The prepared part is placed on the magnetic mating contact in the placement head and this is introduced into the galvanizing cell. The galvanizing cell is placed in the apparatus and the process is started. The primary crown is filled with plastic and the magnetic contact rod with its thin uninsulated side embedded in the plastic. The surface to be plated is coated with conductive silver and a connection drawn from the surface to the rod. The prepared part is placed on the magnetic mating contact in the placement head and this is introduced into the galvanizing cell. The galvanizing cell is placed in the apparatus and the process is started. Result The Galvanokrone meets all quality requirements. Handling is extremely easy, safe and fast. The Galvanokrone meets all quality requirements. Handling is extremely easy, safe and fast.

Claims (13)

1. Apparatus for electrodeposition of shaped dental parts, such as skeletons for crowns, inlays, bridges and the like, having at least one current/voltage source and electrodes which can be arranged in a vessel that can be filled with an electrolyte, wherein

   - there is at least one magnetic connecting means, which comprises two parts (5; 14) which interact with one another through magnetic force, for producing the electrical contact for the electrodeposition between at least one electrode (1) and the current/voltage source,

   - one part (14) of the magnetic connecting means is assigned to the current/voltage source, and one part (5) of the magnetic connecting means is assigned to one end (3) of a rod-like electrode (1),

   - the end (2) of the rod-like electrode (1) without magnetic connecting means is intended for connection to at least one model or part that is to be coated, and

   - the electrode (1) is provided, on its outer surfaces, with an electrically non-conducting coating, the surface (7) which is provided for contact with the current/voltage source and the end (2) of the electrode without magnetic connecting means being free of such a coating.
2. Apparatus according to Claim 1, characterized in that the part (5) of the magnetic connecting means is arranged in the electrode (1) in a sleeve-like receptacle (4).
3. Apparatus according to Claim 1 or 2, characterized in that the magnetic connecting means comprises two magnets (5; 14).
4. Apparatus according to Claim 1 or 2, characterized in that the magnetic connecting means comprises a magnet and a magnetizable metal part.
5. Apparatus according to Claim 3 or Claim 4, characterized in that the magnet has a round cross-sectional area.
6. Apparatus according to one of the preceding claims, characterized in that the part (14) of the magnetic connecting means assigned to the current/voltage source, in particular the magnet, is assigned to a head or cover part which, during the electrodeposition, is located above the vessel that can be filled with the electrolyte and at which the electrodes are preferably also arranged.
7. Apparatus according to one of the preceding claims, characterized in that the magnet (14) is arranged in a sleeve-like component (11).
8. Electrode (1) for electrodeposition of shaped dental parts, such as skeletons for crowns, inlays, bridges and the like, characterized in that it is of rod-like design and one of its ends (3) is assigned one part (5) of a two-part magnetic connecting means, wherein its end (2) without magnetic connecting means is intended for connection to at least one model or part that is to be coated and it is provided, on its outer surfaces, with an electrically non-conducting coating, the surface (7) which is provided for contact with a current/voltage source and the end of the electrode without magnetic connecting means being free of such a coating.
9. Electrode according to Claim 8, characterized in that the end (3) with magnetic connecting means is the end assigned to a current/voltage source during the electrodeposition.
10. Electrode according to Claim 8 or Claim 9, characterized in that the part (5) of the magnetic connecting means is a magnet (5).
11. Electrode according to Claim 10, characterized in that the magnet (5) is arranged in a sleeve-like receptacle (4) in the electrode (1), it preferably being possible for this receptacle to be closed off by a cover part (6).
12. Electrode according to one of Claims 8 to 11, characterized in that the end (2) of the electrode (1) without magnetic connecting means has a smaller cross-sectional area than the end (3) of the electrode (1) with magnetic connecting means, the end without magnetic connecting means preferably narrowing conically or tapering to a point.
13. Electrode according to one of Claims 8 to 12, characterized in that the electrically nonconductive coating is a plastic coating.

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