AU604999B2 - Measuring corrosivity - Google Patents

Description

11 COqIONWEALTH OF AUSTRALIA PATENTS ACT 1 0 ell% COMLP-LETE S P E C I1F I CA T 1 0_N FOR OFFICE USE: Class Int.Class Application Number: Lotdged: Complete Specification Lodged: Accepted: Published: oPriority: Related Art: Eiflndmr~tsin' xs Q.t 1' r Q~ 0 *Name of Applicant: ,Address of Applicant: Actual Inventor: CATOLEUM PTY. LIMITED Anderson Street, Botany, New South Wales 2019, Australia Narayanaswamy Krithivasan 0 Address for Service: SHELSTON WATERS, 55 Clarence Street# Sydney Complete Specification for the Invention entitled: "MIEASURING CORROSIVITY" The following statement is a full description of this invention, including the best method of performinq it known to us:- 1- Complete of P! 608]. dated 24th December, 1987 900.42 7 Fee: $60.00 LODGED AT SUB-OFFiCE 2T i fE1fl7 1 2 41 i: NT OFFICE e DOLLARS in "il i:: i This invention concerns apparatus and a method for indicating the corroded metal content of liquid coolants in automotive engines, locomotive engines, marine engines, leopard tanks and industrial cooling systems. When installed in a cooling system it allows continuous indication and monitoring of the corroded metal content while the coolant is in use.

One of the most common causes of automotive engine breakdown is corrosion of the cooling system components.

The components themselves may be corroded to a sufficient extent to cause them to fail. Alternatively, corrosion products deposited in other parts of the system may reduce 0 the cooling efficiency of the system, due to their o o. insulating properties. Corrosion damdge may also result o 0 0 O in leakage of the coolant. Either through the 0 00 do° inefficiency of some corrosion inhibitor formulations or So through failure of the inhibitor, catastrophic corrosion of aluminium alloy engine components is not an uncommon occurrence. One major factor in this problem is known to 0o0e be a general lack of awareness of *)per coolant system o0000

O

0 4 maintenance and its importance. Corrosion inhibitors S<e included in coolant systems are not, is general, replenished frequently enough to maintain their effectiveness; and the coolant level is often topped up 0 with pure water thus diluting the inhibitor.

0 0 In the past the effectiveness of a coolant Qorrosion inhibitor has only been determinable by extracting a sample of the coolant and testing it in the laboratory.

a 1 i

I

j 2 ii I -I i seal, wltnass or legalisetlon).

To THE COMMISSIONER OF PATENTS.

SHELSTON WATERS PATENT ATTORNEYS CLARENCE STREET. SYDNEY

AUSTRALIA

Cables: 'Valid' S'jiinn. TeIr.Y' 74112? I 1 y j The cost of this test is greater than the cost of replacing the coolant in most vehicles, which together with the lack of immediacy makes it an unattractive procedure. Also the coolant sample may carry dissolved metals which were present in the coolant circuit prior to the addition of corrosion inhibitor, and hence give misleading results.

A corrosivity measuring system has previously been proposed in which use is made of the fact that some corrosion inhibitors have an influence on the polarization characteristics of metals which they I Scf passivate. This technique involves maasuring the open tt c Scircuit voltage of the metal, which is related to the polarization, which in turn is related to the r"r concentration of inhibitor ions present in the coolant.

Ideally this method requires a measurement to be made in respect of each metal in the system for which an inhibitor has been added. But, it has also been proposed to measure the potential of a steel clad aluminium (galvanic couple) electrode with respect to a silver reference V< electrode; since steel and aluminium have been considered to be the most important metals in automotive applications.

According to a first aspect of the invention there is t provided a liquid cooling system corrosion sensor to provide an indication of the corroded metal content of a liquid coolant in use in a cooling system, the sensor comprising a b:metalic couple having two bodies of different metals or alloys separated by an insulating material, suitable for immersion in the liquid, conducting -3-

S

leads respectively connected with each of the bodies to extend t. an accessible location exterior to the cooling system whereby the current generated by the couple can be measured by instrumentation connected to the leads at the accessible location.

According to a second aspect of the invention there is provided a method for indicating the corroded metal content of liquid coolant while in use in a cooling system; the method comprising the steps of installing a bimetallic couple having two bodies of different metals or alloys separated by an insulating material within the t, 0 cooling system, a conducting lead being connected to each- S body; arranging the remote ends of the leads outside the «cooling system; submerging the bimetallic couple in the vg t l liquid coolant; connecting instrumentation between the t c t Ct, remote ends of the leads; and measuring the current generated by the couple by the instrumentation.

The instrumentation comprises either an on-board 44.t circuit which compares the current generated with a pre-set reference current and outputs an indication when j the current generated exceeds the reference on the control console, or, a remote circuit releasably attached between the leads which measures the current generated and outputs t t t, an indication of the current level.

The present invention, when in use, continuously i monitors the corrosivity of the coolant and provides an immediate indication as desired. It makes use of the fact that corrosion is greatest at the interi.aces between 4 different metals that are in contact. For example it has been recognised that a cast iron/altmi7iniu interface is subject to the greatest corrosion in automoti're engines fitted with aluminium alloy heads, and that monitoring the behaviour of this metal couple will provide a warning useful in respect of all others. Accordingly the two bodies of the bimetallic couple are proferably cast iron and aluminium for the above chosen example. Alternatively it has been found that metal couples such as steel/graphite, cast iron/graphite cast iron/solder, and solder/graphite will also provide a useful warning in appropriate cooling systems.

0 Furthermore the invention makes use of a bimetallic 0o0o o couple of standardized dimensions and of any shape and 0 design. This couple is installed within the coolant 0 6 °oo" system, preferably permanently submerged in the coolant, 0° °0 and generates a current proportional to the corroded metal content irrespective of the system in which it is installed. The invention thus has utility in any cooling system in which a fluid coolant is employed.

0o o 00 The preferred embodiment of the invention will now be o oa described, by way of example only, with reference to the accompanying drawings, in which: Sfigure 1 is a schematic illustration of a system o o o 0. embodying the invention installed in a car fitted with an 0 0P aluminium alloy engine head; figure 2 is a circuit diagram of instrufnentation associated with some embodiments of the invention; and figure 3 is a circuit diagram of alternative instrumentation associated with some embodiments of the invention.

Referring now to figure 1 a corrosion sensor comprising a galvanic couple 1 is installed in the cooling system at a convenient location where it will, under normal operating conditions, be submerged in the coolant fluid. Couple 1 comprises a first metal body 2 and a second metal body 3 of a different metal to body 2.

00 oo "10 Preferably body 2 will be cast iron and body 3 aluminium.

Do 00 0 a The two metal bodies are separated by an insulator 4 such 0 00 o oa as a teflon body. The galvanic current produced across 0 00 oo°° the couple is directly related to the corroded metal 0 0 0 06 content, and therefore the corrosivity of the coolant; thus the couple provides an accurate measure of the corrosivity.

0 In the embodiment shown, electrical wires 5 and 6, of negligible resistance, are attached ono to each metal 0000 0o0 body. The wires are soldered to the metal bodies by solder 7, and the joints are encapsulated in non-corrosive oaooo0 and high temperature resistant resin 8. Wires 5 and 6 o 0 oooo extend out of the cooling system, say by passing through the joint where a pipe is clipped onto a metal part.

Wires 5 and 6 end in electrical terminals 9 and 10 in the engine compartment. The terminals may for instance lie in a junction box.

An instrumentation module 11 has signal input leads 12 and 13 connScted to terminals 9 and 10 respectively.

Leads 12 ard 13 may be permanently secured to the 6 terminals 9 and 10 or may be releasably secured as required. When the leads are permanently secured, the instrumentation device may be permanently installed in the vehicle, say in the engine compartment. Alternatively the terminals 9 and 10 may be left accessible in the engine compartment until the engine is serviced, when a portable instrumentation module may be temporarily connected to the terminals in order to determine the corrosivity of the coolant.

Instrumentation module 11 is connected to a DC electrical power supply 34 which may, for instance, be the vehicle battery or a dry cell battery. An output lead extends from module 11 to a output terminal 16. An output device, for instance a warning light and/or meter is connected to terminal 16 and is installed in the dashboard. Alternatively, a warning light and/ot meter may be provided in a portable instrument which, in use, is connected to terminal 16, Referring now to figure 2 a version of the instrumentation module 11 suitable for permanent installation in a vehicle will be described. Terminals 17 and 18 are connected to the positive and negative side of the on-board vehicle battery 14. Power from these rails supplies the operational amplifiers 19 and 20 and biases the input by virtue of resistor network 21, 22, 23 And 24. Input leads 12 and 13 are connected to the senser as previously described.

7' L I--L The senser operates such that the cast iron side will be at a positive potential with respect to the aluminium side, thus lead 12 will be at a positive potential with respect to lead 13. The galvanic current generated is converted to a voltage by feedback resistor 25. This voltage, appearing on line 27, is then compared with a pre-set voltage appearing on line 26. Operational amplifier 20 acts as a bi-stable comparator which changes state depending on the relative magnitudes of the voltage o 0 10 inputs on input lines 26 and 27. This means that as soon 00 00 0 0 0 0 0,0 as the voltage appearing on line 27 exceeds the voltage 0 00 G OO 0 0o appearing on line 26 comparator 20 changes state and a 0 00 0a o positive voltage appears at the output of comparator and at output terminal 16. The positive output voltage at terminal 16 is used to drive an output device, which 0ooe comprises a resistor 28 connected in series with a LED and ooo 0 mounted in the vehicle dashboard. When the voltage on line 26 is greater than the voltage on line 27 the output 0 of comparator 20 is negative and LED 29 is off.

The sensitivity of the device is controlled by resistor 24 which may be selected to provide a suitable 0 threshold level.

Referring now to figure 3 a more sophisticated version of the instrumentation 11 will be described. This version is also suitable for permanent installation in the vehicle dashboard, but owing to its greater complexity aid expense it is preferred at present, for use in a portable unit. AS such it may be releasably connected to the 8permanently installed galvanic couple 1 as required. As before leads 12 and 13 are connected to terminals 9 and and the galvanic current generated is converted to a voltage by feedback resistor 30 connected around operation amplifier 31. The output voltage on line 32 is compared by comparator 33 with a reference voltage on line 34. The reference voltage is pre-set by potentiometer arrangement A LED warning light display 29, similar to that described previously, indicates when the galvanic current exceeds the reference threshold. The output device also includes a digital meter 36 which is connected either to line 32 or line 34. When connected to line 34 digital meter 36 reads the galvanic current produced by the sensor. When connected to line 34 digital meter 36 reads the reference current.

The ivention, although described above with reference to specific embodiments, may of course be embodied in many other forms. For instance, the sensor may be rectangular or square-shaped in elevation and blade-like so it may be installed in the wall of a pipe.

In which case it may have small extensions to penetrate the wall of the pipe and connect with external leads.

Alternatively the sensor may be inserted into the stem of a piece which is connected into the coolant circuit.

It should be appreciated that the invention provides a novel and commercially important solution to a long standing problem.

9

Claims (14)

1. A liquid cooling system corrosion sensor to provide an indication of the corroded metal content of a liquid coolant in use in a cooling system, said sensor comprising a bimetallic couple having two bodies of different metals or alloys separated by an insulating material, suitable for immersion in said liquid, conducting leads respectively connected with each of said bodies to extend to an accessible location exterior to said cooling system oo whereby the current generated by said couple can be 0 1 o measured by instrumentation connected to said leads at 0 0# 009t said accessible location. oo0 I

2. A sensor as claimed in Claim 1 wherein the two bodies of the bimetallic couple are of cast iron and aluminium respectively.

3. A sensor as claimed in Claim 1 wherein the two bodies oo" of the bimetallic couple are of cast iron and solder 0000 respectively. o

4. A sensor as claimed in Claim 1 wherein the two bodies of the bimetallic couple are of steel and graphite oooa respectively. 0 O 0oo

5. A sensor as claimed in Claim 1 wherein the two bodies of the bimetallic couple are of cast iron and graphite respectively.

6. A sensor as claimed in Claim 1 wherein the two bodies of the bimetallic couple are of solder and graphite respectively.

7. A sensor as claimed in Claim 1 wherein the bimetallic l l 1 1 (K"bt:i couple is permanently submerged in the coolant.

8. A sensor as claimed in Claim 1 wherein the instrumentation comprises a circuit which compares the current generated with a pre-set reference current and outputs an indication when the current generated exceeds the reference.

9. A sensor as claimed in Claim 8 wherein the instrumentation is releasably attached between the leads when in use.

A sensor as claimed in Claim 1 wherein the bodies have sharp extensions which penetrate the wall of a pipe of the cooling system and are connected to the leads externally of the cooling system. «0 4

11. A sensor as claimed in Claim 1 wherein the apparatus 0 inc3ldes a piece which, in use, may be inserted into the cooling system, the bimetallic couple being in the stem of the

12. A method for indicating the corroded metal content of coo liquid coolant while in use in a cooling system; said oq method comprising the steps of installing a bimetallic couple having two bodies of different metals or alloys o separated by an insulating material within the cooling system, a conducting lead being connected to each body; o arranging the remote ends of said conducting leads outside said cooling system; submerging said bimetallic couple in the liquid coolant; connecting instrumentation between said remote ends of the leads; and measuring the current generated by said couple by the instrumentation. 11 L i-i i i "L -i i -i

13. A sensor substantially as hereinbefore described with reference to the accompanyinq iins

14. A method substantially as hereinbefore described with reference to t,-he accompanying drawings. DATED thign day of 1990 CATOLEUM PTY. LTD Attorney: LEON K. ALLEN Fellow Institute of Patent Attorneys of Australia of SHELST'ON WATERS L0 0 4 0Q 9 0 6* 0 04 Q 0+ be 4 004 t 000f 0 -12