Abstract:
Disclosed articles as results of a microarc oxidation process, or plurality thereof, which are not limited by size, specifically by certain dimensions of their size, such as their length. Different sections or surfaces of articles of the invention may be subjected to a microarc oxidation process at any given time, such as by gradually subjecting a surface of an article to a microarc oxidation process, or such as by sequentially subjecting different sections of an articles to a microarc oxidation process. Further-more, disclosed are methods for manufacturing of articles of the invention, or otherwise for subjecting articles of the invention to a microarc oxidation process, or plurality thereof. In some examples, tubes of above 6 meter in length may be coated according to methods of the invention. The coating of said tubes may be beneficial for desalination applications. In other examples, only grooves of pulleys are coated. Further disclosed are articles which underwent a microarc oxidation process, or plurality thereof, which included different solution, optionally by utilizing a solution modulator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. application Ser. No. 13/981,064 filed Jul. 22, 2013, which is a 371 of PCT/IB11/52997 filed Jul. 6, 2011, which claims priority from U.S. Provisional Patent Application No. 61/361539 filed Jul. 6, 2010, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to the field of microarc oxidation (or simply “microarc”) in general and to manufacturing articles by microarc oxidation processes in particular. 
       BACKGROUND OF THE INVENTION 
       [0003]    Microarc (or “plasma electrolytic oxidation”) is known in the art for processing valve metals (e.g. aluminum, magnesium, titanium, etc.), such as altering external surfaces of articles made of alloys of said metals (or otherwise containing said metals). As microarc processes consume relatively high amounts of energy, a major resource contributing to their costs is electricity, in direct relation to the measurements or dimensions or size of surfaces undergoing such process. Furthermore, the larger the surface that is subjected to microarc process at any given time—the larger the current density required for the process. Hence, a bigger power supply is necessary for larger surfaces, and so the cost of such a power supply is drastically higher. It is for these reasons that it is extremely difficult or demanding (such as in cost, operation complexity, etc.) to perform microarc processes on very large parts (or “articles”). For articles or parts that are larger than a certain size, it is commercially impossible or impractical to perform microarc processes on their entire surface, or on large sections thereof. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides articles (or “parts”) which are the products of microarc processes, and methods which facilitate production or manufacturing of said articles. The invention otherwise provides methods of performing microarc processes, or of manufacturing articles by utilizing microarc processes. 
         [0005]    An object of the invention is to provide cost-efficient or commercially viable methods for producing or manufacturing articles by utilizing microarc processes. Specifically, said articles may be virtually unlimited in size (i.e. may essentially have any size). Accordingly, in some methods of the invention, only a certain section (or plurality thereof) of an article undergoes a microarc process at any given time. Similarly, some articles of the invention have undergone a microarc process (or plurality thereof), wherein only a certain section (or plurality thereof) of said articles was subjected to said process at any given time. In some methods, an article (or plurality thereof) gradually undergoes a microarc process (or plurality thereof), such that different sections of said articles are sequentially subjected to said process. Similarly, some articles of the invention have gradually undergone a microarc process (or plurality thereof), such that different sections of said articles were sequentially subjected to said process. 
         [0006]    Another object of the invention is to provide methods for performing microarc processes on articles which are larger than the largest articles on which it is known in the art that microarc processes are performed. Some articles of the invention can virtually have any size (e.g. tubes of any length), or specifically a dimension of any size. Otherwise, some articles of the invention may be unlimited in size. Similarly, in some methods of the invention, an article (or plurality thereof) which is not limited in size (e.g. size of a specific dimension, such as length) undergoes a microarc process (or plurality thereof). 
         [0007]    Another object of the invention is to provide articles which result in a transition between different microarc processes, or between multiple periods of a microarc process. Optionally, said transition may be characterized by change in a solution, or exchange between different solutions, utilized for a microarc process or plurality thereof. The invention further provides methods for producing or manufacturing such articles. 
         [0008]    Another object of the invention is to provide tubes (or “pipes”) of any length, which may have been subjected to a microarc process (or plurality thereof), for the purpose of being utilized for desalination systems. 
         [0009]    Another object of the invention is to provide pulleys which a section thereof (or plurality of sections thereof), such as the groove, may have been subjected to a microarc process (or plurality thereof), for the purpose of superior surface properties of said section. 
         [0010]    Another object of the invention is to provide a method to subject an article having any size of external surface (or in other words “surface area”), such as above 30 squared decimeters, or specifically above 60 squared decimeters, without utilizing current density which is above 10 ampere, or more specifically above 100 ampere. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0011]    The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
           [0012]      FIG. 1A  shows a perspective view of a contraption of manufacturing of the invention; 
           [0013]      FIG. 1B  shows a perspective view of the contraption of manufacturing from  FIG. 1A  at a different step; 
           [0014]      FIG. 2A  shows a perspective view of a contraption of manufacturing of the invention; 
           [0015]      FIG. 2B  shows a cross-section view of the contraption of manufacturing from  FIG. 2A ; 
           [0016]      FIG. 3A  shows a perspective view of a contraption of manufacturing of the invention; 
           [0017]      FIG. 3B  shows a cross-section view of the contraption of manufacturing from  FIG. 3A ; 
           [0018]      FIG. 3C  shows a cross-section view of a contraption similar to the contraptions shown in  FIGS. 3A &amp; 3B ; 
           [0019]      FIG. 4A  shows a solution modulator of the invention; 
           [0020]      FIG. 4B  shows a cross section of an article of the invention; 
       
    
    
       [0021]    The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]      FIG. 1A  shows a perspective view of a contraption  100  in which a tube  102  undergoes (or “is subjected to”) a microarc oxidation (or simply “microarc”) process. Contraption  100  may be a device or machine or apparatus or system of the invention, which includes a container  104 . Tube  102  may be a tube of any length, which may pass through container  104 . Specifically, tube  102  may be longer than the length of container  104 , whereas a section of the tube may be inside the container and a different section (or plurality thereof) may be outside the container during a microarc process. For example, container  104  may have a length of two meters, whereas tube  102  may have a length of six meters (yet tube  102  may similarly be of any length above six meters), such that a two meter section of the tube may be inside the container. In some methods of the invention, tube  102  may pass through container  104  during a microarc process. In accordance with the last example, a two meter section of tube  102  may be inside the container at a given time of a microarc process (similarly to the shown in  FIG. 1A  where a section of tube  102  is inside the container), while a different 2 meter section of the tube may be inside the container at a different time. 
         [0023]    In  FIG. 1A , container  104  is shown containing a solution  106  in which the section of tube  102  which is inside the container is immersed. Solution  106  is the solution in which a microarc process (or plurality thereof) may take place (on the section of tube  102  that is immersed in it). For a microarc process, tube  102  is in contact with a connection  108   a  which connects it to an electric current, essentially making tube  102  an anode. Additionally, a connection  108   b  is in contact with a cathode  108   c  which is dipped in solution  106  (otherwise immersed in it). Accordingly, a microarc process may occur (otherwise be performed) on the surface of the section of tube  102  which is immersed in solution  106  (i.e. the surface of the section is subjected to said microarc process). 
         [0024]    In accordance with the shown in  FIG. 1A , during a microarc process (and/or before), a solution may be streamed into container  104  through a pipe  112   a,  and drained from container  104  into a pipe  112   b.  In some embodiments of contraption  100 , pipe  112   a  and pipe  112   b  are both part of a circulation system for a solution (e.g. solution  106 ), such as for cooling said solution outside container  104  and streaming it back into container  104 . Optionally, said circulation system (i.e. the circulation system including pipes  112   a,b ) further includes a solution modulator  114 . Solution modulator may be any part, section, unit or module of contraption  100  which facilitates changing (or “altering”) the solution in container  104  (see ref. a solution modulator  400  in  FIG. 4A ), such that a microarc process (or plurality thereof) utilizes different solutions during different periods. For example, solution  106  may be utilized for a microarc process while passing through a circulation system of contraption  100  (e.g. from container  104  through pipe  112   b ) in which there is solution modulator  114  which may alter solution  106  (e.g. by adding or removing (also “subtracting”) a solvent or a solute), whereas the altered solution may then be utilized for a subsequent microarc process or otherwise for a different period of the same microarc process. 
         [0025]    For a method for performing a microarc process on tube  102 , contraption  100  may include an apparatus  110  (e.g. a robot mechanism) for moving tube  102  through container  104 , such as by pushing the tube or pulling the tube. Accordingly, apparatus  110  may facilitates motion of tube  102  such that a different section of the tube is inside container  104  at any given time. Optionally, the movement of tube  102  by apparatus  110  through container  104  is continuous, such that the tube passes through the container during a microarc process (inside solution  106 ) at a fixed (or “steady”) rate (or “pace”, or “speed”) of motion, or alternatively at a changing rate of motion. For example, apparatus  110  may push tube  102  through container  104  at a rate of half a meter per twenty minutes (i.e. twenty minutes is the period of time in which half a meter of length of tube  102  passes through container  104 ). 
         [0026]    Note that in  FIG. 1A  there is shown a surface  102   a  of tube  102  (shown in the figure outside container  104 ) which is not being subjected to a microarc process, and a surface  102   b  (shown in the figure inside container  104 , specifically inside solution  106 ) which is being subjected to a microarc process. 
         [0027]    Referring now to  FIG. 1B , there is shown contraption  100  at a different step of a method for a microarc process (or plurality thereof) performed on tube  102 . In  FIG. 1B , tube  102  is shown as pushed from its position in  FIG. 1A  to a position shown in  FIG. 1B , optionally by apparatus  110 , as described above. Accordingly, a different surface  102   b ′ of tube  102  (as opposed to surface  102   b  as shown in  FIG. 1A ) is shown inside container  104  and may be undergoing (or “is subjected to”) a microarc process inside solution  104 . Further accordingly, a different surface  102   a ′ of tube  102  (as opposed to surface  102   a  as shown in  FIG. 1A ) is shown outside container  104 , not undergoing a microarc process. Further accordingly, a surface  102   c  (which was inside container  104  when tube  102  was in the position shown in  FIG. 1A ) is shown in  FIG. 1B  outside container  104  (e.g. as it has been pushed out of the container), after it has been subjected to a microarc process (when it was inside container  104 ). Accordingly, surface  102  may be coated by a ceramic coating (e.g. which was generated in the aforementioned microarc process inside container  104 ). 
         [0028]    Following the above, contraption  100  may facilitate subjecting a tube of any length (e.g. 5 meters or above) to a microarc process (or plurality thereof), whereas said tube may be passed (e.g. pushed or pulled by apparatus  110 ) through a container (e.g. container  104  with solution  106 ) which is preferably shorter than the length of said tube. Accordingly, any number of sections of said tube may be subjected to a microarc process (or plurality thereof) by gradually or sequentially or continuously passing through said container (inside which occurs a microarc process). 
         [0029]    Note that the surfaces of tube  102  shown in  FIG. 1A  and  FIG. 1B  and mentioned above are external surfaces of tube  102 , whereas the surfaces of a tube  202  (see ref.  FIG. 2A  and  FIG. 2B ) shown in  FIG. 2A  and  FIG. 2B  and mentioned below refer to internal surfaces of tube  202  (i.e. surfaces inside the tube). 
         [0030]      FIG. 2A  shows a perspective view of a contraption  200  in which a tube  202  undergoes (or “is subjected to”) a microarc process (or plurality thereof). Inside tube  202  are shown (the tube is illustrated such that a gap (referred numerically as gap  201 ) facilitates view of the inside of the tube, yet it is understood that said gap is merely for the purpose of depiction) panel  204   a  and panel  204   b  which may be any parts (e.g. membranes, walls, etc.) that fit inside the tube to create a closed space between them. Optionally, panels  204   a,b  are connected by a connector  214 , such as a rod inside the aforementioned closed space between them. 
         [0031]    In the aforementioned closed space between panels  204   a,b  may be a solution (not shown, yet may fill said closed space) for facilitating a microarc process inside said closed space, specifically subjecting a surface of tube  202  that surrounds said closed space (shown a surface  202   b  in  FIG. 2A ) to said microarc process. Surface  202   b  is subjected to a microarc process (or plurality thereof) as the aforementioned solution inside the closed space between panels  204   a,b  is held (or “enclosed”) by the panels and fills said closed space between them. Accordingly, only surface  202   b  of tube  202  may undergo a microarc process while surface  202   b  is of a section of the tube which is bordered (or “defined”) by panels  204   a,b  (i.e. while the aforementioned solution filling said closed space is surrounded by surface  202   b  by being held between panels  204   a,b ). Further accordingly, any other surface of the tube (e.g. a surface  202   a  as shown in  FIG. 2A ) is not subjected to a microarc process while panels  204   a,b  create a closed space surrounded by surface  202   b  (and in which may be a solution necessary for said microarc process). 
         [0032]    For a microarc process to occur inside the aforementioned closed space that is between panels  204   a,b  and that is surrounded by surface  202   b,  tube  202  is shown in contact with a connection  208   a  which connects it to an electric current, essentially making tube  202  arm anode. Additionally, a cathode  208   c  is located (or “positioned”, or “installed”) inside the closed space (i.e. between panels  204   a,b ), and accordingly inside a solution that may fill the closed space between panels  204   a,b.  Cathode  208   c  is shown in  FIG. 2A  attached to a connection  208   b  which connects it to an electric current. 
         [0033]    In some embodiments, panel  204   a  is connected to an apparatus  210  which can move panels  204   a,b  inside tube  202  (joint movement may be facilitated by connector  214  connecting the panels) at a fixed or changing pace. For example, apparatus  210  may push panel  204   a  (and optionally also panel  204   b  with it) from one end of tube  202  towards an opposite end. By moving panels  204   a,b,  the closed space between the panels may be surrounded by a surface of a different section of tube  202  (i.e. a different surface at any given time during the moving). Accordingly, a different section of a surface of tube  202  (otherwise a different surface of the tube) may be subjected to a microarc process between panels  204   a,b  at any given time. Optionally, the movement of panels  204   a,b  by apparatus  210  may be steady (i.e. at a fixed speed) so that each section in the path of the movement of the panels may be subjected to a microarc process by a similar duration (or “period of time”). Such movement may be similar to the movement of tube  102  through container  104  of contraption  100  as shown in  FIG. 1A  and  FIG. 1B , and as described above. 
         [0034]    Following the above, a section of any length of a surface inside tube  202  may be gradually subjected to a microarc process (or plurality thereof), as panels  204   a,b  move through the tube (i.e. along the inside of the tube), whereas between the panels  204   a,b  may be a closed space in which there may be a solution facilitating said microarc process on a surface of tube  202  that surrounds said closed space (or otherwise that is bordered by the panels). 
         [0035]    In some embodiments, a pipe  212   a  is leading (or “streaming”) a solution to the closed space between panels  204   a, b,  whereas a pipe  212   b  is draining a solution from said closed space, as shown in  FIG. 2A  (shown pipes  212   a,b  attached to panel  204   b ). Optionally, pipes  212   a,b  are parts of the same solution-circulating system. As known in the art for microarc processes, a solution-circulating system is sometimes required, such as for cooling a solution (which may be heated during a microarc process). Similarly to the described for contraption  100 , a solution modulator (e.g. solution modulator  114  as shown in  FIG. 1A  and  FIG. 1B ) may be included in a solution-circulating system which may also includes pipes  212   a,b,  such that a solution inside the aforementioned closed space between panels  204   a,b  may be monitored and/or changed (or “altered”, or “modified”). 
         [0036]    While apparatus  210  is shown and described connected to panel  204   a,  and pipes  212   a,b  are shown connected to panel  204   b,  it is made clear that the scope of the invention is not limited to which panel or how each of the above elements are connected. For example, pipes  212   a,b  and apparatus  210  may be connected to the same panel (e.g. to panel  204   b ). 
         [0037]    Referring now to  FIG. 2B , there is shown a cross-section view of contraption  200 , in accordance with the described above for  FIG. 2A . In  FIG. 2B  there is numbered a space  220  which is a closed space between panel  204   a  and panel  204   b,  such as described above for a closed space between the panels, in which a microarc process (or plurality hereof) may occur, specifically performed on a surface of tube  202  that surrounds space  220  (i.e. that is bordered by panels  204   a,b;  e.g. surface  202   b ). Said microarc process may be facilitated by a solution filling space  220 , such as held between panels  204   a,b  and surrounded by surface  202   b.    
         [0038]      FIG. 3A  shows a perspective view of a contraption  300  in which a pulley  302  undergoes (or “is subjected to”) a microarc process (or plurality thereof). More specifically, it may be desired that only the groove of pulley  302  (shown a groove  302   b  in  FIG. 3A ) will be subjected to a microarc process, whereas the process will be prevented from the rest of the pulley. This may be, for example, for the purpose of reducing cost of manufacturing, such as the cost of the microarc processes required for generating a ceramic coating on groove  302   b  of pulley  302 , which may be lower than the cost of generating such a coating on the groove and on the rest of the pulley. 
         [0039]    In  FIG. 3A , contraption  300  is shown to include a container  304  inside which is a solution  306 . Solution  306  fills container  304  up to a certain height, whereas pulley  302  is dipped in the solution to a certain extent. In  FIG. 3A  there is shown the bottom of pulley  302  dipped in solution  306  such that the bottom of groove  302   b  is immersed in the solution. Additionally, the external surfaces of the bottom of the flanges between which is groove  302   b  may also be immersed in solution  306 , yet the pulley is positioned such that its center is outside the solution (and accordingly is not subjected to any microarc process inside the solution). A section of pulley  302  which is not immersed in solution  306  and thus is not subjected to a microarc process is numbered in  FIG. 3A  as  302   a.  In some embodiments, the external surfaces of the flanges which define groove  302   b  (i.e. the groove is between them) may be covered by covers  322  (one cover  322  is shown in  FIG. 3A  covering the external surface of one flange, whereas another cover  322 ′ is shown in  FIG. 3B  in addition to said one cover  322  that is shown in  FIG. 3A ). Covers  322  may isolate the aforementioned external surfaces of the flanges from any microarc process occurring inside solution  306 , so that said external surfaces are prevented from being subjected to said microarc process. 
         [0040]    For positioning pulley  302  as described above, it is shown in  FIG. 3A  pulley  302  hoisted (or “installed”) on a rod  314  which is conductive and attached to a connection  308   a  which is a connection to an electric current, thus connecting pulley  302  to an electric current and essentially making it an anode. However, it is made clear that hoisting pulley  302  on a rod does not limit the scope of the invention to only such a construction or way for dipping pulley  302  in solution  306  to a certain extent (i.e. not fully immersing the pulley in the solution). 
         [0041]    Similarly to the described above for other contraption of the invention, contraption  300  may include a cathode  308   c  which may be dipped in solution  306  and attached to a connector  308   b  which connects it to an electric current, thus facilitating a microarc process inside the solution. Further similarly to the described above, contraption  300  may include a pipe  312   a  which streams a solution into container  304 , and a pipe  312   b  which drains a solution (optionally the same solution) from the container. 
         [0042]    In some embodiments, rod  314  may be connected to an apparatus  310  which rotates it, whereas pulley  302 , as hoisted on the rod, rotates respectively. For example, apparatus  310  may be a robot which rotates rod  314  and accordingly pulley  302  as it is hoisted on rod  314 . By rotating pulley  302 , a different section of the surface of groove  302   b  is immersed by solution  306  at any given time, and so a different section of the surface of the groove may be subjected to a microarc process at any given time. Accordingly, the surface of groove  302   b  may gradually undergo a microarc process (or plurality thereof), such as by rotating pulley  302  and thus having sections of the surface of the groove sequentially immersed in solution  306  (where a microarc process may occur). For example, apparatus  310  may rotate rod  314  and respectively pulley  302  at a steady or changing pace such that a different section of the surface of groove  302   b  is immersed in solution  306  at any given moment, thus a different section of the surface of the groove is subjected to a microarc process in the solution at any given moment (or “at any given time”). 
         [0043]    In some embodiments and in some methods, an entire rotation (i.e. of 360 degrees) of pulley  302  (e.g. by apparatus  310 ) may repeat itself such that different sections of the surface of groove  302   b  are repeatedly immersed in solution  306 , thus undergoing a microarc process (or plurality thereof) multiple times. Note that from our findings, in some cases, such a repetition does not have a substantial (or any) effect of the continuity of the coating on a groove of a pulley resulted from a microarc process as described herein. For example, it may be difficult to distinguish between a surface of a groove of a pulley which has been completely immersed in a solution during a microarc process and a surface of a groove of a pulley which was dipped in a solution and rotated in accordance with the described above. 
         [0044]    In  FIG. 3A , similarly to the described for contraption  100  and contraption  200  regarding streaming of solution and draining of solution, contraption  300  may include a pipe  312   a  which streams solution into container  304 , and a pipe  312   b  which drains solution from container  304 . 
         [0045]    Referring now to  FIG. 3B , there is shown a cross-section view of contraption  300 , in accordance with the described above for  FIG. 3A . 
         [0046]    Referring now to  FIG. 3C , there is shown a cross-section view of a contraption  330 , similar to the described above for contraption  300  (certain elements of contraption  300  are not shown in  FIG. 3C  yet it is made clear that they may be included in contraption  330 ). In contraption  330 , a pulley  332 , a pulley  334  and a pulley  336  are joined together (e.g. physically attached as they are installed on rod  314 ), and also dipped in solution  306 , such that only the surface of their grooves is exposed to the solution, whereas the external surface of the flanges of said grooves is not exposed to the solution (e.g. by being tightly attached to the external surface of flanges of another pulley&#39;s groove). However, the external surface of one of the flanges of the groove of pulley  332  and the external surface of one of the flanges of the groove of pulley  336  may be exposed to the solution, as shown in  FIG. 3C . Alternatively, the external surface of one of the flanges of the groove of pulley  332  and the external surface of one of the flanges of the groove of pulley  336  may be covered by covers  322  (e.g. one by cover  322  and another by cover  322 ′), such as shown in  FIG. 3B  the external surface of the flanges of groove  302   b  covered by covers  322  (i.e. the surface of one of the flanges by cover  322 , and the surface of the other flange by cover  322 ′). 
         [0047]    In  FIG. 4A  there is shown a solution modulator  400 , similar to solution modulator  114  in  FIG. 1A . Accordingly, solution modulator  400  facilitates any change of a solution, or exchange between solutions. Optionally, solution modulator  400  includes a container  404  in which changes (or “alterations”, or “modifications”) in a solution occur, or in which one solution is exchanged by another solution. A solution which was or is utilized for (or “took part in”) a microarc process may be streamed to container  404  through a pipe  414   a,  whereas a modified solution (or a different solution) may be streamed out of (or “drained from”) container  404  through a pipe  414   b.  Pipes  414   a,b  may be part of a solution-circulation system of a contraption of the invention or of any contraption for microarc oxidation processes. Optionally, solution modulator  400  may include a monitor  414  for obtaining information about a solution inside container  404 . For example, monitor  414  may check which temperature a solution is at, and/or which pH. Accordingly, for the same example, solution modulator  400  may change the temperature and pH of said solution, such as by utilizing a cooling system or unit or module, and/or by adding any amount of a certain substance to a solution (e.g. more of the solvent or more of the solute of the solution). 
         [0048]    In some embodiments, solution modulator  400  may facilitate changing a solution for a microarc process for plurality thereof), or a part (or “period”) thereof, such that a microarc process, or plurality thereof, may utilize different solutions, or otherwise be composed of periods at each of which a different solution is utilized (i.e. an article is immersed in different solutions in different periods of a microarc process). For example, a first solution may be utilized for subjecting an article to a microarc process (e.g. said article may be immersed in said solution, in a contraption that facilitates microarc processes), whereas said first solution may be streamed to solution modulator  400  (e.g. through pipe  412   a ), whereat it may undergo changes or replaced altogether by a second solution. Said second solution (or the changed first solution) may then be streamed from solution modulator  400  (e.g. through pipe  412   b ) to be utilized for a microarc process which the same aforementioned article may undergo subsequently. For a more specific example, a certain contraption (e.g. contraption  100 ) may include solution modulator  400 , whereas a tube (e.g. tube  102 ), or a section thereof, may undergoe a microarc process in a container (e.g. container  104 ) filled with a solution (e.g. solution  106 ) which includes a first pigment solute. After a certain period of time, said solution may be added a second pigment solute by solution modulator  400 , such as by said first solution passing through solution modulator  409  (e.g. in a circulation system) and being streamed back to said container (of the aforementioned contraption) in which a microarc process may be performed. Accordingly, said microarc process may be composed of two periods, in the first of which there is present said first pigment solute, whereas in the second of which there is present said second pigment solute (in addition to, or substituting, said first pigment solute). 
         [0049]    In some embodiments, changes in a solution or exchanges between solutions, may be facilitated by s faucet  416   a  and/or by a filter  416   b,  as shown in  FIG. 4A , or by any means known in the art. 
         [0050]    Following the above, a solution modulator of the invention (e.g. solution modulator  400 ) may facilitate any change (or “modification”, or “alteration”) of a solution for a microarc process, or plurality thereof, and/or any replacing (or “switching”, or “swapping”, or “exchanging”) between two or more solutions for a microarc process, or plurality thereof. Otherwise, a solution modulator of the invention may be any part (or “unit”, or “module”) of a contraption or device or apparatus or system for subjecting articles to microarc processes, whereas said solution modulator may facilitate any change in a solution, or any exchanging of solutions, for microarc processes performed by said contraption or device or apparatus or system. It is made clear that a solution modulator of the invention may facilitate change in a solution, or exchanging of solutions, during a microarc process, or otherwise while a microarc process occurs, or at any period along the duration of a microarc process. Accordingly, any changing or exchanging as described above may be transitional or gradual. 
         [0051]    While solution modulator  400  may be shown in  FIG. 4A  and described by the above, it is made clear that a solution modulator of the invention may be any apparatus or device or system, or part or unit or module thereof, which may, by any means known in the art, change (or “alter”, or “modify”) a solution of a microarc process, or exchange solutions of a microarc process (i.e. replace one solution by another). Otherwise, it is made clear that a solution modulator of the invention may change a solution utilized for any microarc process, or plurality thereof, or switch between solutions utilized in different periods of any microarc process. More specifically, it is made clear that the scope of the invention includes any device, apparatus, contraption or system, or unit, part or section thereof, which may be utilized in a microarc process (or plurality thereof) to modify a solution in which said microarc process occurs (or “is performed”), or exchange solutions during said microarc process (by any means known in the art). For example, a microarc process may occur inside a container filled with a first solution, whereas a solution modulator of the invention may stream additional solutes into said first solution, optionally during said microarc process. Alternatively, a solution modulator of the invention may gradually drain said first solution while gradually stream a second solution into said container. 
         [0052]    Following the above, some methods of the invention may include steps in which different solutions may be utilized in (or “for”) the same microarc process, or may include steps of changing a solution (or switching between solutions) during a microarc process, or plurality thereof. Accordingly, some articles of the invention may include a coating which is a result of a microarc process for which (or “in which”) different solutions were utilized, or for which modifications were made in a solution that was utilized to subject an article (or plurality thereof) to said microarc process. 
         [0053]    In  FIG. 4B  there is shown a cross-section view of a surface of an article  440  (generally, the face of the article is shown at the bottom of the figure, whereas towards the top of the figure is the inside of the body of the article), whereas said article was subjected to a microarc process composed of two periods, the first of which was performed in a first solution, whereas the second of which was performed in a second solution. Article  440  may have originally been made of a material  442  (e.g. aluminum), whereas after the aforementioned microarc process—material  442  generally makes the internal volume of article  440  (i.e. the inside of the body of the article which was not subjected to any microarc process). As shown in  FIG. 4B , a material  444  (e.g. alumina) may have been formed on (otherwise “out of”) material  442  during the first period of said microarc process which was performed in said first solution. Additionally, a material  446  (e.g. alumina containing a pigment) may have been formed on (otherwise “out of”) material  444  during the second period of said microarc process which was performed in said second solution. Optionally, material  446  was additionally formed from matter in said second solution, such as from a pigment solute (in addition to matter from material  444 ). As shown in  FIG. 4B , materials  442 ,  444  and  446  may not be exactly defined as layers, yet may exhibit a transition (e.g. a gradient pattern) in article  440 , in accordance with a gradual exchange between the aforementioned first solution and the aforementioned second solution in the aforementioned microarc process. 
         [0054]    Following the above, a surface of an article of the invention (up to a certain depth inside the volume of said article) may be made of several layers, or of a transition pattern of several materials (e.g. a gradient of compositions of materials), which were formed during different periods of a microarc process in which different solutions were utilized. Said different periods may have been phased into each other gradually (or by any transition sequence), such as in case said different solutions were switched from one into another gradually. 
         [0055]    Note that while the described herein refers to microarc oxidation (or “plasma electrolytic oxidation”), similarly within the scope of the invention are related processes, such as plasma electrolytic nitriding, plasma electrolytic carburizing, plasma electrolytic boriding, plasma electrolytic carbonitriding, etc. 
         [0056]    While the described herein is for certain embodiments of devices of the invention featuring certain elements, it will be appreciated that other embodiments may be included in the scope of the invention which feature different combinations of elements described herein, and their equivalences as known in the art. 
         [0057]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.