AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT ELECTRO-CHEMICAL WELD CLEANING SYSTEM The following statement is a full description of this invention, including the best method of performing it known to me.
Title of the Invention ELECTRO-CHEMICAL WELD CLEANING SYSTEM Field of the Invention 5 The invention relates to improvements in portable systems of stainless steel polishing and weld discolouration removal. Background of the Invention .0 Electropolishing is a process related to controlled electrolytic removal of metal, oxides and other contaminants using an electro-chemical process. The metal component, composed of stainless steel or other alloys, is in contact with an electrolyte solution and electric current is passed through the component. In essence this process is the reverse of electroplating. During electroplating material is 15 deposited onto the component; Electropolishing mechanically restructures the surface of the metal by expelling electrons from the exposed surface causing a smoothing reaction. Electropolishing descales the surface, removing oxides and impurities and leaves a sterile, bright, passive finish. For many people involved in stainless steel manufacturing, the use of and 20 exposure to dangerous chemicals such as hydrofluoric acid based pastes and gels, are a common occurrence. There have been other proposals for safer methods of 1 stainless steel weld cleaning/electropolishing, but these are expensive systems which fail to recognise that one major component of those systems, the high current power supply, unnecessarily contributes significantly to their high cost, thus keeping safer methods for stainless steel weld cleaning and electropolishing out of the 5 financial reach of many stainless steel manufacturers. It is an object of the invention to provide an improved portable system for metal polishing and weld discolouration removal. Summary of the Invention .0 The present invention provides a portable system for electropolishing of metal and weld discolouration removal from surfaces comprising : a delivery component adapted to deliver a suitable electrolyte solution to a cathodic handpiece electrode; an anode electrode connected to a workpiece; 15 a means of cooling the said cathodic electrode via a closed system of water reticulation; and a low voltage direct current power supply wherein the power supply is sourced from an existing AC/DC or DC welding machine. 2 Preferably, the power supply is sourced from a DC welding machine. Preferably, the electrolyte solution is selected from the group consisting of phosphoric, orthophosphoric, citric and acetic acids. Preferably, the electrolyte solution comprises about 40 to 50% 5 orthophosphoric acid and 15 to 20% acetic acid. A method of electropolishing comprising a system according to the present invention. Brief Description of the drawings .0 Figure 1 shows an embodiment of the electrochemical weld cleaning system Detailed Description of the Invention The present invention provides a portable system for electropolishing of metal and weld discolouration removal from surfaces. In particular, the present invention 15 utilizes a portable boxed fluid delivery and cooling unit which incorporates an electrolyte delivery system, a re-circulating water cooling system, an inexpensive mains powered power supply to provide electrical energy only to power these two fluid systems at low voltage and current, and a hand held electrode which connects to both the fluid delivery/cooling unit, and to a suitable existing DC power supply 20 such as a DC electric welding machine. 3 Figure 1 illustrates an embodiment according to the present invention related to the electrochemical weld cleaning system. A metal enclosure houses a switching ATX power supply, water reservoir, water pump (pump 1), electrolyte reservoir and electrolyte pump (pump 2). 5 Pump 1 recirculates water as a cooling medium to the cathodic electrode, from the water reservoir and back, through suitable flexible hosing. Pump 2 delivers an electrolyte solution to the electrode, from the electrolyte reservoir, via suitable acid resistant flexible hose. .0 A flexible electric cable electrically connects the cathodic electrode to an existing electric welding machine's negative electrode terminal. A similar cable electrically connects the workpiece to the welding machine's positive earth terminal. 15 A boot made of fiberglass woven cloth covers the working surfaces of the electrode to provide (a) a non-conductive insulating shield between the metal parts of the electrode and the workpiece surface, thus preventing direct metal to metal contact between the electrode and the workpiece, and (b) to provide a medium of electrolyte saturation, through which electric current may sufficiently pass for the 20 purposes of electrochemical metal cleaning/polishing. 4 A toggle switch (SW1) on the front panel of the metal enclosure controls the switching ON/OFF of the ATX power supply, by completing a circuit between the PWR and COMMON terminals provided in said ATX power supply. Another toggle switch (SW2) on the front panel of the metal enclosure controls the 12 volt dc supply 5 current to Pump 1. Still another switch (SW3), which is located at the electrode handpiece, controls the 24 volt DC supply current to Pump 2, thus allowing for on demand electrolyte delivery to the cathodic electrode/boot arrangement. In another version, SW1, SW2 and SW3 separately, may each be used to control .0 a secondary current to indicator lights mounted on the front panel of the apparatus, which are indicative of the various electrical states of the apparatus, namely "POWER ON", "COOLING PUMP ON" and "ELECTROLYTE DELIVERY ON", respectively. .5 In still another version, adjustable potentiometers mounted on the front panel may be used in series to SW2 and SW3 separately, to enable differential rates of flow for coolant and electrolyte respectively. In yet another version, the shape of the electrode box will be altered, to be arrow point shaped at the front edge, so as to enable the device to reach inside internal 20 corners of fabricated items. 5 The present invention attempts to overcome the problem of the high cost of portable electro-chemical weld cleaning and electropolishing of metals, by providing a fluid delivery system which (1) delivers a suitable electrolyte solution to the cathodic electrode handpiece, (2) provides a means of cooling the said cathodic 5 electrode via a closed system of water reticulation, and (3) retro-fits to existing DC welding machines, so as to utilize the existing DC welder as an energy source, to provide the electrical energy required for the well established electro-chemical process involved, thus negating the need for a high current power supply to originate from the apparatus itself. The key point is that many manufacturers already have the .o power source required for the process of electropolishing, in the form of DC welding machines. The system according to the present invention allows manufacturers to realise this potential, at a fraction of the cost of purchasing a stand-alone unit as offered by inventions based on the prior art. .s Thus, the problem of using an expensive apparatus for supply of direct current can be overcome with the present invention, which recognises that the electrical current required for the electro-chemical weld cleaning and/or electropolishing process, can be sourced from existing direct current (DC) welding machines which provide satisfactorily adjustable direct current for electro-chemical weld cleaning and 20 electropolishing of stainless steel. In one embodiment, an electric welder output is in the range of 20 to 50 volts, with current variable from zero or close to zero amps, to approximately 150 to 350 6 amps, depending on the welder itself. More recently, portable electric welders entering the market have additional features such as pulsed output, and AC output with adjustable AC balance control, specifically for tig welding aluminium. These features of newer more advanced electric welders can also be utilized for the electro 5 chemical metal cleaning/polishing process. Preferably, for the electropolishing process, current applied at 25-30 amps provides sufficient energy for the electro chemical process, whilst still being low enough for the water reticulation cooling system to keep heat under control and prevent premature wearing out of the fiberglass boot. .0 The present invention also utilizes various electrolyte solutions, containing varying ratios and strengths of phosphoric, orthophosphoric, citric and acetic acids, which are used for differing purposes of weld discolouration removal and for electropolishing the parent metal. .s The range of ratio of composition of orthophosphoric and acetic acids that can be used are fairly wide. In one embodiment, 40 to 50% Orthophosphoric acid is combined with 15 to 20% acetic acid, and which provides optimum results for electropolishing. Furthermore, the same solution, diluted in a 1:1 ratio with demineralised water, provides a useful and efficient weld-cleaning electrolyte. 20 The electrolyte delivery system comprises a stainless steel or plastic electrolyte reservoir of approximately one litre capacity, a low voltage peristaltic fluid pump to deliver the electrolyte solution to the electrode handpiece and suitable acid resistant 7 flexible hosing and clamps to connect between the components. The electrical circuit controlling the electrolyte fluid pump includes low voltage electrical cabling to the electrode handpiece and a suitable spring loaded or toggle electrical switch to turn the electrolyte delivery pump on and off remotely, at a distance from the metal 5 enclosure. The cooling system consists of a stainless steel or plastic water reservoir of approximately eight litres capacity, a low voltage in-line or centrifugal pump to deliver cooling water to the electrode handpiece, and suitable flexible hosing and clamps for .o connecting the recirculating water between the reservoir, pump and electrode handpiece. The power supply used to power the pumps is a mains powered ATX power supply, as used in desktop computers, supplying low voltage and low current DC .s electrical energy to the various components, via switching components on the front panel of the enclosure and the electrode handpiece. Various signaling lights on the front panel of the box unit may also be utilized to indicate the various states the system, including 'Mains power on/off', 'Water cooling on/off' and 'Electrolyte delivery on/off'. 20 The hand held electrode, or 'handpiece', comprises a small stainless steel fabricated enclosed box of approximately 10mm height, 25mm width and 50mm length, with inlet and outlet tubes for cooling water to flow through accordingly. A 8 threaded stainless steel rod is welded on or about the top of the electrode, to which a suitable flexible copper cored insulated cable may be electrically and mechanically fastened to the electrode through a suitable electrical cable eyelet and stainless steel nut and flat washer. The other end of this copper cable is connected electrically and 5 mechanically to the negative terminal on the suitably chosen low voltage high current DC power source, such as an existing DC welding machine. The positive terminal of this power source is connected to the workpiece through a typical welding earth clamp arrangement. A small stainless steel tube passes through the centre of the electrode from bottom to top, welded and flush on the bottom and welded and .o protruding on top, sufficient to connect to the electrolyte delivery tube. A 'boot' of sewn woven fiberglass cloth is attached to the 'foot' of the electrode, fully covering the base and sides, to facilitate electrical contact between the electrode and workpiece through drenching with electrolyte and the electro-chemical cleaning/polishing process. The fiberglass cloth boot also acts to insulate the .5 workpiece from direct metal to metal contact with the electrode, which would otherwise result in unwanted contact arc marks on the workpiece. The electrolyte delivery pump and reservoir, the cooling system pump and reservoir, and the low voltage ATX power supply are housed in a fabricated metal enclosure box, to protect the components from damage. Suitable openings exist for checking 20 and filling the reservoirs when required. Various venting spaces in the enclosure exist to facilitate air flow through the box to help keep cool the internal components. A port at the rear of the box unit also provides access to the ATX power supply mains cable plug socket and to provide sufficient clear space for the ATX in-built 9 cooling fan. On the front face of the enclosure is a faceplate with two electrical switching controls, and three illuminating indicator lights. The first electrical switch connects to the 'power on' and 'common' terminals of the ATX power supply. When closed, this circuit switches on the ATX power supply, thus providing power for the 5 fluid driving systems. The second switch closes a 12volt circuit for the cooling water pump. Two wires run from the ATX power supply '-12v' and '+12v' terminals, through the peristaltic electrolyte pump, to a switching mechanism on the handpiece, thus providing an available 24 volts to control the electrolyte pump remotely from the handpiece as required. .0 To use the system, the apparatus is first placed on a level surface adjacent to the suitably chosen high current power supply. The coolant level is then checked, and when required, filled with clean potable water. The electrolyte level must then be checked to ensure adequate electrolyte is available to the pump, for the job at hand. .5 A fiberglass cloth boot must then be attached to the electrode foot, ensuring the base and sides are satisfactorily insulated. The copper cable from the handpiece is then connected to the negative terminal of the chosen high current DC power supply, and the current control of that device is set to its minimum level, or 15 amps. This current control should never exceed 30 to 40 amps, as doing so will result in 20 overheating of the electrode, and premature wearing out of the fiberglass cloth boot. The mains connector cable is then used to connect the apparatus' ATX power supply to the mains supply. The 'power on' switch on the faceplate of the metal enclosure is then switched on, followed immediately by turning on the coolant pump. The 10 electrode handpiece must then be primed for use. To do this, the switch on the handpiece must be switched on or depressed until the boot is saturated with electrolyte. Next, the high current DC power supply (DC positive) earth lead is used to connect the high current DC power supply to the job, and the high current DC 5 power supply switched on. Whilst allowing electrolyte solution to be pumped into the handpiece, the handpiece is gently lowered onto the surface of the job and slowly moved across the surface to be treated without applying pressure. Supply current to the handpiece may be increased slowly, until the electrolyte begins a very gentle 'sizzle'. Rapid boiling of the electrolyte is an indication that supply current to the .o handpiece is too high, and will result in premature failure of the fiberglass cloth boot. The handpiece is slowly and uniformly moved across the surface of the job to be treated, and repeated until the desired surface finish is achieved. Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. .5 11