Abstract:
A sacrificial marine anode with a water proof encased current tester to alert an operator of proper connectivity, current status of the cathodic protection system for an associated marine structure, and status of current tester power supply is disclosed.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   None. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   None. 
   REFERENCE TO A MICRO-FICHE APPENDIX 
   None. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is generally related to a supplemental cathodic protection system for submersed metal portions of marine structures to mitigate corrosion thereto and to prolong the life of existing anodes installed on the structures. 
   2. Description of the Related Art 
   A search of the prior art located the following United States patents which are believed to be representative of the present state of the prior art: U.S. Pat. No. 6,547,952 B1, issued Apr. 15, 2003, U.S. Pat. No. 6,228,238 B1, issued May 8, 2001, U.S. Pat. No. 5,384,020, issued Jan. 24, 1995, U.S. Pat. No. 5,747,892, issued May 5, 1998, U.S. Pat. No. 5,716,248, issued Feb. 10, 1998, U.S. Pat. No. 5,627,414, issued May 6, 1997, U.S. Pat. No. 4,322,633, issued Mar. 30, 1982, and U.S. Pat. No. 3,953,742, issued Apr. 27, 1976. 
   BRIEF SUMMARY OF THE INVENTION 
   Corrosion is an electrochemical process accompanied by the flow of electrical current. Corrosion occurs when the following elements are present: an electrolyte or medium which conducts current by ion flow, such as water; an anode or metal which corrodes to protect another metal, such as a propeller shaft, rudder, or hull on a boat; a cathode or metal which is protected by another metal, such as bronze and stainless steel fittings on a boat; and a metallic pathway or medium which conducts current by electron flow, such as the hull, bonding systems, electrical systems on a boat. 
   Galvanic corrosion is the most common form of corrosion that attacks the integrity of boating structures and marine equipment. Galvanic corrosion develops when different types of metals are electrically common by submersion into water. For example, if a boat equipped with a steel rudder that is bonded to a bronze or stainless steel fitting is placed into water, the steel rudder will corrode. The steel rudder becomes the anode, while more noble metals such as bronze or stainless steel become cathodes. The water acts as the electrolyte. The metallic path is the metallic hull of the boat or the boat&#39;s bonding system. 
   Cathodic protection is the process of reversing the corrosion current to stop the damaging corrosion process. One type of cathodic protection known as galvanic cathodic protection is achieved by placing a type of metal into the water with the boat and connecting it to the boat&#39;s metallic parts. Metals such as aluminum or zinc are less noble than the other boat metals and therefore act as anodes when connected to the metal parts of the boat. 
   Zinc anodes have been long used for mitigating corrosion on metal marine structures. These devices typically consist of a bare ingot of zinc mounted to the hull, propeller shaft or rudder, or similar metallic elements of a boat. These anodes are designed to provide protection from galvanic corrosion on the boat. Additionally, bare zinc anodes attached to a long wire that comprises a clamp at the unattached end have been used to supplement the mounted zinc anode systems. 
   Anodes of the art do not provide replaceable anode elements or protective casings to house the anode during use. Likewise, anodes in the art do not provide current monitoring circuitry to ensure proper deployment or attachment to provide adequate protective cathodic current flow protection to the metal marine structures. 
   It is therefore desirable to provide an improved apparatus for supplemental cathodic protection of submerged metal portions of marine structures to mitigate corrosion thereto which provides a combined anode and current tester. 
   It is an object of the present invention to provide an improved anode and current tester which indicates when the anode has been deployed correctly and a connection to the submerged metal portions of a marine structure is made in a satisfactory manner. 
   It is a further objective of the present invention to provide an improved anode and current tester which indicates when protective cathodic protection current is flowing. 
   It is still a further objective of the present invention to provide an improved anode and current tester which is easily installed and used by a lay operator. 
   It is yet a further objective of the present invention to provide an improved anode and current tester apparatus which does not damage surfaces that come in contact with the apparatus. 
   Yet another object of the present invention is to provide an improved anode and current tester apparatus which will prolong the life of existing anodes installed on marine structures. 
   The apparatus of the present invention consists of a replaceable anode element and a current tester element. The anode element comprises a cylindrical anode element consisting of a marine grade alloy selected from the group consisting of aluminum, magnesium, zinc, or the like. 
   The replaceable anode is housed inside a slotted plastic casing. The slotting provides contact between the anode and an electrolyte, such as seawater. The casing protects the anode and the metal marine structure from damage resulting from their contact due to wave action, or damage resulting from the anode contacting others surfaces, namely dropping the anode onto a surface such as a boat deck. 
   The current tester is housed inside a water proof enclosure. It comprises different colored light emitting diode (LED) lamps or other similar light sources to serve as self check mechanism for proper connection and adequate flow of cathodic protection current. By depressing a switch on the current tester, the operator is alerted as to whether or not the anode has been deployed correctly and attached to the metal marine structure in a satisfactory manner to register a resultant flow of protective cathodic protection current. 
   Other features, advantages, and objects of the present invention will become apparent with reference to the following description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a not to scale depiction of the elements of an embodiment of the present invention. 
       FIG. 2  is a not to scale depiction of one application of an embodiment of the present invention connected to the cathodic protection circuit of a marine vessel. 
       FIG. 3  is an electrical schematic of a circuit suitable for the current tester element of an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention combines a marine anode housed within an anode casing which allows anode contact with an electrolyte when the casing is submerged within the electrolyte. The anode is disposed in noncontact association with a metal structure to be protected by a wire of suitably coated and insulated materials. Circuitry housed in a water proof casing is connected in series with the anode and metal structure by attachment to the wire. This circuitry has a self-contained direct current power source, and provides the operator with switched testing of current strength, proper connectivity of the marine anode, and flow of cathodic protection current. Once an anode has been corrosively consumed, it is easily replaced within the anode casing by a new anode of like material. 
   As shown in  FIG. 1 , a preferred embodiment of the present invention  100  comprises a 1.5 inch diameter by 12 inch or 24 inch long slotted or otherwise perforated, cylindrical anode casing  10  housing a detached 1.2 inch diameter by 12 inch or 24 inch long replaceable anode element  20 . The anode element is made from a marine grade alloy material selected from the group consisting of aluminum, magnesium, zinc, or the like. The slotted casing  10  has a plurality of slotted openings  16 , or similar access, along the casing wall to allow free flow of electrolyte through the casing slots or openings and provide electrolytic contact with the housed anode element  20 . The slotted casing  10  is further defined by one open, threaded end to receive a threaded cap  40  for easy anode access and replacement. The other end of the slotted casing  10  is closed by a permanent cap  30 . The anode casing  10 , and the caps  30  and  40  are made from durable grade polyvinylchloride, or similar materials, suitable for withstanding moderate external impact and the internal forces of the metal anode in turbulent electrolytic environments. The anode casing  10  with caps  30  and  40  thus provides protection from the anode impacting decking surfaces or boat sidewalls while in use. 
   The anode assembly of a preferred embodiment of the present invention,  FIGS. 1 and 2 , is supplied with a ⅛ inch diameter vinyl coated, stainless steel/insulated copper wire in two lengths. One wire length  50  which connects the anode element  20  to the current tester  72  is approximately twenty-five feet in length. The second wire length  90  connects the current tester  72  to a stainless steel connector  60  for connection to a metal marine structure bonding or cathodic protection system. The stainless steel connector  60  for a preferred embodiment of the present invention is an alligator type clamp. The second wire length can be tailored for the operator&#39;s convenience, but it typically ranges from approximately eighteen to twenty-four inches. 
   The threaded cap  40  on one end of the slotted or otherwise perforated anode casing  10  provides access for the attachment of the vinyl coated, stainless steel/insulated copper wire  50  to one end of the anode element  20  through an opening in the threaded cap end. 
   When an anode is corrosively consumed or otherwise ceases to provide adequate cathodic protection, it is easily replaced by another anode of like material by insertion into the slotted or otherwise perforated anode casing  10 . This process requires only the opening of the anode casing  10  at the threaded cap  40  end of the anode casing  10  by removal of the threaded cap  40 . The threaded end cap is positioned a distance along the copper wire  50  through the opening in the cap end. The consumed anode is detached from the vinyl coated, stainless steel/insulated copper wire  50 , which is in turn connected to one end of the new or replacement anode element  20 . One end of the new or replacement anode element  20  is attached to the copper wire  50 . The replacement anode element  20  with copper wire  50  attached is then inserted into the anode casing  10  along the casing&#39;s longitudinal axis. The threaded cap  40  is re-secured to the anode casing  10  and the apparatus of the present invention is ready to be reapplied to the marine structure to provide supplemental cathodic protection. 
   As further depicted in  FIGS. 1 and 3 , the current tester  70  of the present invention is installed in series with the anode assembly near the clamp end of the wire. The current tester  70  is housed inside a 1 inch diameter by 4 inch length of transparent vinyl tubing  72  with two plastic, water proof end caps  74  and  76 . It is critical to the proper function of the present invention that the sides of the vinyl tubing  72  provide sufficient compression pliability to allow an operator to depress the switch  78  of the current tester circuitry by squeezing the tubing  72  from the exterior of the tubing walls. This external activation of the switch  78  allows the operator to confirm the adequacy of the current tester circuitry power supply, connectivity of the anode and current tester, and current flow to the intended structure(s). The preferred embodiment of the present invention uses an internal, direct current battery pack  306  depicted generally in  FIG. 3 , as its power supply. One end cap  74  provides water proof access from the length of vinyl coated, stainless steel/insulated copper wire  50  which is attached to one end of the anode element  20 . The other end cap  76  provides water proof access from the length of vinyl coated, stainless steel/insulated copper wire  50  which is attached to one end of the anode element by an alligator type clamp  60  with insulated handles. The current tester  70  is thus made water proof when enclosed within the capped, vinyl tubing housing. 
   The tester further comprises the necessary electronic circuitry used to detect cathodic protection current flow from the anode to the metal marine structure to be protected. Housed with the tester within the water proof assembly described above is the current supply for the electronic circuitry. The tester provides a manual switch  78  accessible from the housing exterior by operator applied pressure and a red LED signal  80  to check the current tester battery life,  FIGS. 1 and 3 . The tester further provides a green LED signal  82  to check if the proper connection is made to the metal marine structure to be protected and if a flow of cathodic protection current of 5 mA or greater is detected,  FIGS. 1 and 3 . 
     FIG. 2  depicts use of an embodiment of the apparatus of the present invention to provide protection to the rear portion of a marine structure,  200 , having a stern drive unit  234  with propeller  240 . The wire portion  50  of at least one apparatus of the present invention is secured to the unsubmerged portion of the structure so that at least one housed anode portion  10  hangs three to four feet below the bottom of the submerged portion of the structure,  200 . In this fashion, the housed anode is within the electrolyte solution, but reamins above any mud or vegetation present in, and any sea floor or similar bottom surface below, the electrolyte. 
   As shown in  FIG. 2 , the current tester  70  is connected in series to the vessel&#39;s battery  212  at the negative post and the anode  10  by lengths of vinyl coated, stainless steel/insulated copper wire,  90  and  50 , respectively. An alligator type clamp connector  60  secures the length of wire from the tester  70  to the battery  212 . The marine vessel&#39;s stern drive unit  234  is grounded to the hull  244  and connected to the battery  212  by line  256 . The housed anode portion  10  is disposed in noncontact association with the metal elements of the marine structure  200  to be protected. 
     FIG. 3  is an electrical schematic of a circuit suitable for performing the current testing functions of the present invention. In the following description of  FIG. 3 , the component values and identification refer to one particularly preferred embodiment of the circuit and are not limiting to the present invention. As well understood by those in the art, the absolute magnitudes of the components and the particular types of components used in the circuit of  FIG. 3  can be changed without adversely affecting the operation of the present invention as long as certain relationships and characteristics of the components are maintained. 
     FIG. 3  shows the line from the anode  50  and the line from the structure to be protected  90 . The operator then applies pressure to the transparent portion of the current tester to depress the internal switch or push button  78 . 
   As the button  78 , a normally open push button switch, is pressed, current flows from the battery  306  into the test circuit. A voltage divider consisting of two resistors,  308  and  309 , divides voltage from the battery  306  to a pre-set reference voltage. The switch  78  also provides power to the lm324 type operational amplifiers,  301 - 303 . Three of the four operational amplifiers built into the lm324 type chip,  301 - 303 , are used in this embodiment of the present invention. The first,  301 , as a primary stage comparator across the shunt resistor  307  to detect current flow. Its output is fed into the second two switch stage operational amplifiers,  302  and  303 , amplifying the signal to determine its value relative the reference voltage. If the output value is below the reference voltage, one of the operational amplifiers  302  is switched to high, and the other  303  is low. If the output value is above the reference voltage, these operational amplifier switched values are reversed. This embodiment of a circuitry suitable for the present invention is wired such that if the output of the primary stage operational amplifier  301  is below the reference voltage, the red LED  80  is illuminated and the green LED is not illuminated. If the output of the primary stage operational amplifier  301  is above the reference voltage, the red LED  80  is not illuminated and the green LED is illuminated. The switching point or current detection threshold is determined by the values and placement of the voltage divider resistors,  308  and  309 , and the value of the shunt resistor  307 . A current limiting resistor  310  is in series with the LED&#39;s,  80  and  82 , to prolong battery  306  and LED life. 
   Prior to anode deployment, a red LED  304  glow indicates that the current tester power supply  306  is adequate but that no current is flowing through the anode  10 ,  FIGS. 2 and 3 . After anode deployment, i.e.,  FIG. 2 , the operator again applies pressure to the transparent portion of the current tester to depress the internal switch or push button  78 . A green LED  305  glow indicates current flow through the anode  10 , signifying proper apparatus connection to the vessel  200  and operation of the anode circuitry. In the present circuitry, the green LED  305  lights up at about 5 mA. One or more LED&#39;s of different colors can be added to this circuitry (not shown), triggered by differing current levels to indicate the level of current output from the anode. 
   Accordingly, an improved marine anode with current tester has been disclosed. 
   With respect to the above description then, it is to be understood and realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings, circuit schematics, and described in the specification are intended to be encompassed by the present invention. 
   A latitude of modification, change and substitution is intended in the foregoing disclosure, and in some instances some features of the invention will be employed without a corresponding use of other features. Therefore, it is appropriate that the appended claims be considered broadly and in a manner consistent with the spirit and scope of the invention disclosed herein.