AU5595401A - A corrosion protection arrangement - Google Patents

Description

11089

ORIGINAL

Complete Specification Applicant: Inventor: Title: Address for Service: Electronic Rust Prevention Systems (Australia) Pty Ltd John Mason Fuller A corrosion protection arrangement LESICAR PERRIN, 49 Wright Street, Adelaide, South Australia 5000, Australia The following statement is a full description of this invention, including the best method of performing it known to me/us: A corrosion protection arrangement The present invention relates to a corrosion protection arrangement and a voltage source means for use therein. The corrosion protection arrangement has particular application to vehicles to provide rust prevention or minimisation of rust occurrence for that vehicle. The arrangement may however also be used to protect other metallic objects including fixed constructions such as bridges..

BACKGROUND OF THE INVENTION The following discussion of corrosion and previously proposed arrangements are discussed in simplified terms.

It is well known that some metals from which objects are made are susceptible to corrosion.

A common example is the rusting of iron-based metals including steel, but there are many more examples. In these corrosion processes typically a redox reaction occurs where the metal gives up an electron during the reaction. The use of paints and similar coatings attempt to prevent redox reactions occurring but where the coating becomes damaged or 15 degraded such reactions can still occur.

It has been previously proposed to use cathodic protection systems having an anode and a cathode, being the metal object, connected to an electrical power supply. Generally speaking, these systems treat the metal object to be protected from oxidation as the cathode of an electrolysis circuit. These methods normally require an anode, a source of electric energy, and an aqueous solution. The anode and cathode must be in contact with the aqueous solution. The source of electric energy is then used to create a current between the anode and the cathode. As the source of electric energy provides electrons to the cathode (which is the metal object being protected from oxidation), the substances in the aqueous S•solution that have sufficient reduction potential to be reduced acquire the electrons provided by the electric current, rather than electrons from the metal, and are reduced. The rate of oxidation of the cathode (the metal object being protected from oxidation) is significantly reduced because the majority of the electrons needed for reduction of the chemical substances in the aqueous solution (the environment surrounding the metal object being protected) are provided by the electric current, rather than the metal in the cathode. Where the aqueous solution does not extend between the anode and cathode then the circuit is incomplete.

In US Patent No. 4,767,512 to Cowatch et al disclosed is a capacitative coupling being formed between an anode and the metallic object that acts as a cathode. Paint or another coating forms the dielectric and so a capacitor is formed. The anode is relatively small compared with the object. Unipolar voltage pulses are supplied across the capacitor. This is stated to effect charging and discharging of the capacitor, which in turn spreads electrons over the surface of the object and so provides electrons to be used in place of those from the metal object for any redox reaction.

Prior known circuits, excepting simple D.C volt systems such as 12 V motor vehicle systems, can however be complex and involve a considerable number of parts and may therefore involve considerable expense.

It is a proposed object of this invention to provide a corrosion protection arrangement or a voltage source means to obviate or minimise at least one of the aforementioned problems, or at least provide the public with a useful choice.

SUMMARY OF THE INVENTION 15 The invention may be said to reside, not necessarily in the broadest or only form, in a voltage source means for a corrosion protection arrangement, said corrosion protection arrangement being for a dielectric coated metallic corrosion susceptible object, the voltage source means including a collapsing magnetic field voltage up converter having an output terminal, the collapsing magnetic field voltage up converter being adapted to be connected to electrical power supply means providing an input voltage and to convert the input voltage into a positive output voltage of magnitude higher than the input voltage relative to the common, and the output terminal and the objects being adapted to be connected to a first terminal of a capacitance formed between the first terminal and the object separated by the dielectric coating.

In another form the invention may be said to reside, again not necessarily in the broadest or only form, in a corrosion protection arrangement being for a dielectric coated metallic corrosion susceptible object, the voltage source means including: electrical power supply means adapted to provide an input voltage relative to a common and said common being electrically connected to the object; a first terminal of a capacitor formed between the first terminal and the object separated by the dielectric coating; and, a collapsing magnetic field voltage up converter connected to the electrical power supply means by an input terminal and having an output terminal, the collapsing magnetic field voltage up converter being adapted to convert the input voltage into a positive output voltage of magnitude higher than the input voltage relative to the common, and the output terminal electrically connected to the first terminal.

Preferably the collapsing magnetic field voltage up converter may include an inductor and a switching device connected in series between the input terminal and the common, unidirectional means having an anode end connected to the junction between the inductor and the switching device with a cathode end of the unidirectional means being connected to the output terminal, the unidirectional means being adapted to conduct current when the anode end is subject to a higher voltage than that appearing on the cathode end relative to the common, and a storage capacitor connected between the output terminal and either the common or the input terminal. In this form the converter may provide a relatively high voltage with relatively few components and by comparison to known systems circuit complexity and cost may be significantly lower.

In preference the unidirectional means may be a diode. It will be appreciated by those skilled in the art that other devices may be used in place of a diode including switched devices though a diode is a simple device. For example, a transistor may be used with suitable base circuitry.

20 In preference between the anode end and the storage capacitor connected thereto and the output terminal is an impedance adapted to limit current flow out of the output terminal. This can be used to limit any current flow to a safe level so that human beings in contact with the *l 0e*.

anode do no suffer electrocution. Further, the impedance provides short circuit protection to the converter should the anode and cathode become shorted. The impedance may preferably be a resistance adapted to limit current flow due to the positive output voltage out from the output terminal less than In preference the impedance and the storage container are adapted to give the storage capacitor a discharge time constant by current flow through the output terminal greater than 100s. With the switching device operating to charge the storage capacitor at much more frequent intervals than the voltage across the storage capacitor is substantially a constant level.

Advantageously the switch means is a semiconductor-switching device that may be a transistor. Preferably the switching means switches ON and OFF in response to an oscillator control signal applied to a control terminal of the switching means, and the oscillator control signal being generated by an oscillator. The oscillator may preferably be a free running oscillator.

In a yet further form of the invention there is proposed an apparatus for reducing the rate of oxidation of a metal object consisting of an input, a dielectric material adapted to form a dielectric barrier between said input and a surface of a metal object, power means for providing a first voltage to a collapsing magnetic field voltage up converter adapted to convert said first voltage into a second voltage whose magnitude is higher than the first voltage, said second voltage connected to said input, said object connected to the common of said power means.

Preferably power means is a 12V battery. Typically the power means is a vehicle battery such as a truck, car or marine battery.

15 In a still form of the invention there is proposed a process of reducing the rate of oxidation of a dielectrically coated metal object including the steps of: providing an input voltage relative to a common to a collapsing magnetic field voltage up converter, said converter providing an output voltage whose magnitude is larger than the input voltage; 20 connecting said object to the common; connecting said output voltage to a first terminal said first terminal defined as a terminal of a capacitor formed between the first terminal and the object separated by the dielectric coating; and activating said input voltage whereby a current sufficient to provide electrons to reducing chemicals in the environment immediately surrounding said metal object is impressed in said Smetal object.

BRIEF DESCRIPTION OF THE DRAWINGS To assist in the understanding of the invention preferred embodiments will now be described with reference to the accompanying drawings: Figure 1 is a block diagram of the arrangement embodying the present invention; Figure 2 is a block diagram of the collapsing magnetic field up voltage converter; Figure 3 illustrates the converter of the present invention in more detail; and, Figure 4 is a circuit diagram of the converter.

DESCRIPTION OF THE PREFERRED EMBODIMENT The following detailed description of the invention refers to the accompanying drawings.

Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing form the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

For explanative purposes only, the application of the arrangement to a vehicle will be used but it will be appreciated that the arrangement may also be used with other metallic objects ~The corrosion protection arrangement is for a dielectric coated metallic corrosion susceptible object such as a motor vehicle. The vehicle is diagrammatically represented by 1. The 15 arrangement includes electrical power supply means 2 that for a motor vehicle may be a 12 Volt battery as commonly available. The electrical power supply means is adapted to provide an input voltage 3 relative to a common 4. The common is electrically connected to the metal S of the motor vehicle.

Also provided are voltage source means 5 including a first terminal 6 of a capacitance formed between the first terminal and the motor vehicle 1 separated by a dielectric coating 7.

The voltage source means 5 consists of a collapsing magnetic field voltage up converter 8 connected to the electrical power supply means by an input terminal 9 and having an output terminal 10. The collapsing magnetic field voltage up converter 8 is adapted to convert the input voltage 3 into a positive output voltage of magnitude higher than the input voltage relative to the common, and the output terminal 10 is electrically connected to the first terminal 6.

The collapsing magnetic field voltage up converter 8 includes an inductor 11 and a switching means 12 connected in series between the input terminal 9 and the common 4. A unidirectional means 13 being a diode, having an anode end 14 connected to the junction between the inductor 11 and the switching device 12 with a cathode end 15 of the unidirectional means 13 being connected to the output terminal 10. The unidirectional means 13 is adapted to conduct current when the anode end 14 is subject to a higher voltage than that appearing on the cathode end 15 relative to the common 4. A capacitor 16 is connected between the output terminal 10 and the input terminal 9. Those skilled in the art will appreciate that the capacitor could be connected between the output terminal 10 and the common 4.

Between the anode end 14 and the capacitor 16 connected thereto and the output terminal is an impedance 17 which in this case is a resistor adapted to limit current flow out of the output terminal 10. The arrangement is adapted to provide an output voltage of about 600 volts across the capacitor 16. To provide short circuit protection for the circuit and to minimise risk of electrocution to a human, the resistor 17 limits the current to a maximum of about The resistor 17 and the capacitor 16 are adapted to give the capacitor a discharge time constant by current flow through the output terminal greater than 100s. The switching means 15 is a semiconductor transistor. The rate of switching and the conduction period is controlled by free running oscillator 18 which takes the form ofa 555 oscillator as is known to the art 00 producing rectangular pulses. The frequency of switching is 2.5kHz and thus it will be appreciated that the capacitor 17 is essentially maintained charged and that across the output 10 the voltage is essentially D.C. It will be appreciated by those skilled in the art that adjustment of frequency and on conduction times, together with circuit characteristics determines the voltage that is generated across the capacitor.

*o The input voltage line to the converter 8 includes conditioning circuitry 19. Either diode 20 or 21 are included in the input voltage line. These both provide polarity protection for the converter. Where desired diode 20 is used with diode 21, transistor 22, Zenner diode 23 and 25 resistor 24 omitted. This form would typically be used where the power supply is a mains S: connected DC power supply. Alternatively, diode 20 is omitted with diode 21, transistor 22, Zenner diode 23 and resistor 24 included which together form a low input voltage turn off circuit. For a 12 V battery of a vehicle when the voltage drops below a predetermined voltage then due to the Zenner diode and resistor the transistor is switched off and so battery power consumption is minimised.

LED 25, resistor 26, field effect transistor (FET) 28 and Zenner diode 27 provide visual indication when the circuit is operating. The gate of the FET is biased by a voltage divider 29, which is connected across the output. When the output is sufficiently high then the gate 8 is at a voltage to turn the FET on and so caused the LED to light. The voltage divider 29 also ensures that there is some bleeding off of charge across the capacitor and so limits the voltage build up across the capacitor.

In operation the arrangement is connected to first terminal 6 and to the power supply. When the switching means is conducting current build up and flows through the inductor. A magnetic field is created. When the switching means is turning off, then the magnetic field endeavours to maintain the current flow leading to a voltage spike, which forward biases the diode 13 so impressing the voltage across the capacitor. In this way, the capacitor is charged and maintained charged by the converter. The output power requirements are not great and so this form of circuit may be used to convert the 12 Volt battery supply into 600 Volt output. The number of components, cost and complexity of circuitry may be considerably less than other known up voltage converters such as transformers.

It will be appreciated that the characteristics of the inductor, circuit layout and the like may not be fully known. Accordingly, some experimentation may be necessary in adjusting 5 oscillator frequency to control current flow in the inductor and voltage up conversion.

One skilled in the art will therefore appreciate that the present apparatus provides for a capacitive coupler that is held at a constant high voltage, positive with respect to zero Volts, thus inducing a negative with respect to zero Volts electrostatic field on the surface of the object to be protected, that is, at the interface of the dielectric and the object where typically 20 the dielectric is a paint.

Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all 25 equivalent devices and apparatus.

.i S° In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "Including", i.e. the features specified may be associated with further features in various embodiments of the invention.

Claims (16)

1. A voltage source means for a corrosion protection arrangement, said corrosion protection arrangement being for a dielectric coated metallic corrosion susceptible object, the voltage source means including: a collapsing magnetic field voltage up converter having an output terminal, the collapsing magnetic field voltage up converter being adapted to be connected to an electrical power supply means providing an input voltage and converting the input voltage into a positive output voltage of magnitude higher than the input voltage relative to the common, the output terminal connected to a first terminal of a capacitance formed between the first terminal and the object to be protected separated by the dielectric coating.

2. A corrosion protection arrangement being for a dielectric coated metallic corrosion susceptible object, the voltage source means including: an electrical power supply means adapted to provide an input voltage relative to a 15 common, said common being electrically connected to the object; a first terminal of a capacitor formed between the first terminal and the object separated by the dielectric coating; and, a collapsing magnetic field voltage up converter connected to the electrical power supply means by an input terminal and having an output terminal, the collapsing magnetic field voltage up converter being adapted to convert the input voltage into a positive output voltage of magnitude higher than the input voltage relative to the common, the output terminal electrically connected to the first terminal.

3. A corrosion protection arrangement as in claim 2 wherein the collapsing magnetic field voltage up converter includes: 25 an inductor and a switching device connected in series between the input terminal and the common; an unidirectional means having an anode end connected to the junction between the inductor and the switching device with a cathode end of the unidirectional means being connected to the output terminal, the unidirectional means being adapted to conduct current when the anode end is subject to a higher voltage than that appearing on the cathode end relative to the common; and a storage capacitor connected between the output terminal and either the common or the input terminal.

4. A corrosion protection arrangement as in claim 3 wherein said unidirectional means is a diode.

A corrosion protection arrangement as in claim 3 wherein said unidirectional means is a transistor with suitable base circuitry.

6. A corrosion protection arrangement as in any one of claims 2 to 5 further including an impedance adapted to limit current flow out of the output terminal.

7. A corrosion protection arrangement as in claim 6 wherein said impedance and the storage container are adapted to give the storage capacitor a discharge time constant by current flow through the output terminal greater than I00s.

8. A corrosion protection arrangement as in any claim 3 wherein said switching device is a semiconductor-switching device, which may be a transistor.

9. A corrosion protection arrangement as in claim 3 wherein said switching means '*switches ON and OFF in response to an oscillator control signal applied to a control terminal of the switching means, and the oscillator control signal being generated by 15 an oscillator.

A corrosion protection arrangement as in claim 9 wherein said oscillator is a free running oscillator.

11. A corrosion protection arrangement as in any one of claims 2 to 10 wherein said input voltage is 12 Volts.

12. An apparatus for reducing the rate of oxidation of a metal object consisting of an input, a dielectric material adapted to form a dielectric barrier between said input and S.I a surface of a metal object, power means for providing a first voltage to a collapsing magnetic field voltage up converter adapted to convert said first voltage into a second voltage whose magnitude is higher than the first voltage, said second voltage connected to said input, said object connected to the common of said power means.

13. An apparatus as in claim 12 wherein said power means is a 12V battery.

14. A process of reducing the rate of oxidation of a dielectrically coated metal object including the steps of: 11 providing an input voltage relative to a common to a collapsing magnetic field voltage up converter, said converter providing an output voltage whose magnitude is larger than the input voltage; connecting said object to the common; connecting said output voltage to a first terminal said first terminal defined as a terminal of a capacitor formed between the first terminal and the object separated by the dielectric coating; and activating said input voltage whereby a current sufficient to provide electrons to reducing chemicals in the environment immediately surrounding said metal object is impressed in said metal object.

A corrosion protection arrangement substantially as hereinbefore described and with reference to the accompanying drawings.

16. A method of protecting objects against corrosion substantially as hereinbefore described and with reference to the accompanying drawings. SEC Dated this 2 4 th day of July 2001 Joh/r 'QcrsonFunev Pui7 p -E4Pctrcnic Ruot Prvzntien Systcma (Auttrnlia)- yd By their Patent Attorneys LESICAR PERRIN o .o