A WEAR INDICATOR FOR A SACRIFICIAL ANODE AND A SACRIFICIAL ANODE

ASSEMBLY COMPRISING THE SAME

The present invention relates to a wear indicator for use with a sacrificial anode, in particular to a wear indicator for use with a sacrificial anode mounted on the hull of a boat. The present invention also relates to a sacrificial anode assembly comprising the wear indicator, as well as a water borne vessel incorporating the same.

The corrosive effects of a metal in contact with an electrolyte are well known and understood. In summary, when two dissimilar metals are in contact with an electrolyte, such that an electrical connection is made between the metals through the electrolyte, corrosion of the metal having the greater electronegativity occurs.

A common occurrence of this type of corrosion is the corrosive effect of salt water, such as sea water, on the iron or steel hull of a boat or other vessel. Other metals, present in the hull or other fittings in contact with the water, can also suffer from such corrosion. In order to protect the hull and other fittings of the vessel in contact with the water, it is known to secure to the hull of the vessel a metal having a greater electronegativity than the metal of the hull or the fittings, generally referred to as 'cathodic protection ¹ . In this way, the said metal, referred to as a sacrificial anode, acts as the anode in the aforementioned electrolytic process and suffers the corrosive effects, in place of the hull itself or other fittings. While the sacrificial anode acts to reduce or eliminate anodic corrosion of the hull or other fittings, it is itself consumed over a period of time. If allowed to continue, the sacrificial anode would be completely consumed and the hull and other fittings left unprotected. At this point, significant damage can be caused to the vessel which, if left unchecked, is typically difficult if not impossible to repair.

In order to prevent damage occurring to the vessel itself, it is common practice to regularly inspect the sacrificial anodes in place on the hull of the vessel. However, this is not necessarily a simple task, in particular in the case of large boats

or vessels. While it is common practice to remove boats from the water at regular intervals to carry out maintenance, this can be both expensive and time consuming. In general, the removal of a the boat from the water merely to inspect the sacrificial anodes is not time or cost effective and is seldom done. As a result, sacrificial anodes are generally checked and replaced as part of a regular maintenance schedule. One problem with this practice is that the anodes are typically replaced while still serviceable, in order to avoid the risk of the anode being completely consumed and the vessel itself rendered vulnerable to corrosion. Alternatively, and of more concern, situations can arise where the rate of corrosion of the anodes is accelerated, such that the anode is fully consumed before the next scheduled maintenance is reached. Again, this leaves the vessel unprotected and liable to potentially damaging corrosion. Such situations can arise in certain ports and harbours and will typically occur without the operators or crew of the boat or vessel becoming aware.

One solution to this problem is to inspect the hull of the vessel and the sacrificial anodes at shorter intervals than the scheduled maintenance. However, as the anodes are mounted below the water line in order to provide the optimum protection, this generally necessitates the use of divers to inspect the hull and its fittings. This is generally time consuming and expensive. For these reasons, it is rarely carried out.

Accordingly, it would be most advantageous if a means of indicating the wear of sacrificial anodes mounted to the hull of a boat or vessel below the water line without the need either to remove the vessel from the water or to despatch divers to inspect the hull underwater.

Wear indicators for sacrificial anodes are known in the art and several different arrangements and embodiments have been proposed in the past.

DE 41 17 781 A1 discloses a sacrificial anode assembly for fitting to a tank by means of a hollow connection sleeve connected at one end to an anode body. The anode body has a test chamber therein. The second end of the sleeve is connected

to a signal cartridge have a transparent cap. The interior of the signal cartridge contains a device for emitting a signal when the anode is consumed. The device for emitting the signal is a hygroscopic capsule containing an optical indicator, such as a dye, a membrane which deforms upon the ingress of water into the cap, or a push- out pin. The membrane or moveable pin may be arranged to trigger an electrical circuit, to provide an indication of the state of the anode. The sleeve passes through the wall of the tank, providing the visual indication on the exterior of the tank of the state of the anode within the tank.

DE 41 24 930 A1 also concerns a sacrificial anode assembly. The assembly is generally similar to that of DE 41 17 781 A1 , having a hollow sleeve with a device for emitting a signal when the anode has been consumed.

WO 92/12277 discloses a wear indicator for consumable anodes, in particular for water tanks and hot water units. Again, the wear indicator comprises a connecting sleeve having one end connected to a test chamber within the anode. The second end of the connecting sleeve comprises a signal cartridge having a transparent cap. An optical indicator is located within the cap, to provide an optical signal when the anode is consumed. The optical indicator may be a dye, a diaphragm that is displaced under pressure, or a moveable pin.

WO 2004/101851 is also concerned with a wear indicator for a sacrificial anode. The indicator comprises a detector embedded within the anode at a predetermined distance from an exposed surface of the anode before use. The indicator may comprise a visual signal that is activated when the anode has corroded sufficiently to reveal the indicator. The visual signal may be a button that is extended from the surface of the anode by a spring, when the button is released as a result of corrosion of the anode. Alternatively, the indicator may comprise a pair of electrodes, which become electrically connected when exposed by corrosion of the anode surface. A monitoring system may be connected to the indicator, for example to sound an alarm when the wear of the anode has reached a predetermined level. A similar system is disclosed in US 2004/02222084.

While the aforementioned systems of the prior art may provide an adequate means for detecting and indicating the wear of the anode, there is a general reliance on the use of visual indications. The indicators are generally complex, being comprised of a large number of components.

Accordingly, there is a need for an improved wear indicator for a sacrificial anode, in particular one that may be readily applied to a vessel, such as a ship or yacht, in a marine environment and avoids the need to remove the vessel from the water for inspection or to deploy divers to inspect the hull of the vessel below the waterline.

According to a first aspect of the present invention, there is provided a wear indicator for a sacrificial anode of a vessel having a hull, the sacrificial anode being in place on the exterior of the hull of the vessel and which is arranged to expose the wear indicator to light from the exterior of the vessel upon a predetermined level of wear of the anode, the indicator comprising means for providing an indication of light reaching the indicator, thereby indicating wear of the anode to the predetermined level.

In a further aspect, the present invention provides a sacrificial anode assembly for a vessel, the assembly comprising: a sacrificial anode for mounting to the exterior of the hull of the vessel; a wear indicator; the anode being arranged to expose the wear indicator to light from the exterior of the vessel at a predetermined degree of wear of the anode; and means for providing an indication of light reaching the wear indicator, thereby indicating wear of the anode to the predetermined level.

For reasons explained in detail hereinafter, the anode preferably comprises a cavity within the anode disposed at a predetermined distance from the surface of the anode corresponding to a predetermined level of wear of the anode, the wear indicator being exposed to light when the cavity in the anode is exposed due to corrosion or wear of the anode.

The present invention provides a means and method for indicating the wear of a sacrificial anode mounted on the hull of a vessel. As the anode is secured to the exterior of the hull of the vessel, once sufficient corrosion of the anode has taken place to expose the cavity, daylight is allowed to enter the cavity. The devices of the present invention provide an indication of this daylight entering the cavity, to thereby indicate the level of wear of the anode. The invention allows the indication of light to be provided within the vessel, thereby avoiding the need to remove the vessel from the water or deploy divers to inspect the level of wear of the anode.

The invention relies for operation upon the principle that the sacrificial anode is located in a position that receives ambient light or daylight, in at least sufficient amounts to provide an indication of the wear of the anode. As the wear indicator itself or, if present the cavity within the anode, is exposed, through corrosion of the anode, ambient light or daylight impinges on the sensing means and/or enters the cavity. It is this ambient light or daylight that is used to provide an indication of the wear of the anode.

Accordingly, in a further aspect, the present invention provides a method for indicating the condition of a sacrificial anode, the method comprising disposing the anode in a position to receive light and to shield a light indicating means from the said light, the method further comprising allowing the anode to wear so as to remove the shield from the light indicating means at a predetermined degree of wear, whereby the light indicating means provides an indication of light, indicating wear of the anode to at least the predetermined degree.

It has been found that, even though the sacrificial anodes are located on the hull of a vessel below the water line, they generally receive sufficient ambient light, during daylight hours, to provide a clear indication of daylight entering the cavity, when the cavity becomes open to the surroundings. Accordingly, this provides a means for inspecting the condition of the anode during daylight hours. Should insufficient daylight be present at the time of inspection, for example as a result of the

inspection being during the hours of dusk or darkness, light may be provided to the exterior of the hull, for example by use of a lamp or the like.

It is a significant advantage of the wear indicators of the present invention that they may be employed as separate components to the sacrificial anodes. In particular, the wear indicators may be installed in or on the hull of the vessel and sacrificial anodes placed over or around the indicators. As the sacrificial anodes wear and require replacement, they may be removed and replaced without disturbing the wear indicators. This is a significant improvement over the known wear indicator systems that require replacement of the wear indicator with each new sacrificial anode.

Any suitable means may be employed to provide an indication of light revealed by the wear of the anode, to thereby indicate wear of the anode. The present invention provides several specific embodiments to provide the indication.

In one embodiment, the wear indicator employs a bore or aperture extending through the hull from its exterior to the interior of the vessel. The bore or aperture communicates with the anode, most preferably with a cavity formed in the anode, such that wear of the anode exposes the bore or aperture to light, which is visible from the interior of the hull of the vessel. Most preferably the bore or apertures is exposed to light entering the cavity in the anode, which passes through the bore or aperture into the interior of the hull.

In a simple embodiment, the wear indicator of the present invention comprises a transparent plug or cap for the bore or aperture through the hull of the vessel. The plug or cap is mounted to the hull in a watertight manner, to prevent water from entering the hull. When the anode is corroded to the extent that the plug or cap is exposed or a cavity within the anode is exposed and light may enter the cavity, the light will be visible from within the hull through the transparent plug or cap. Thus, a regular inspection of one or more anodes may be carried out by a person from within the vessel simply by looking at the plugs or caps. Those anodes with wear to at least the predetermined degree will be readily identifiable as the light

becomes visible through the plug or cap. At this point, a decision may be made regarding servicing or replacing the respective anode.

In a further embodiment, the wear indicator comprises a sleeve having a bore therethrough for extending through the hull of the vessel. One end of the sleeve is in connection with the anode or, more preferably, with a cavity in the anode, such that the bore opens into the cavity and light entering the cavity may pass along the bore of the sleeve. The sleeve is secured in an aperture or bore in the hull so as to be watertight. The second end of the sleeve extends into the hull of the vessel. The sleeve has at least one seal assembly along its length, whereby water cannot pass along the bore in the sleeve. The seal assembly comprises at least a portion that is transparent, allowing light to pass along the bore in the sleeve. The seal assembly is preferably disposed in at least one end portion of the sleeve. In one preferred embodiment, a seal assembly is provided at each end of the sleeve. A suitable seal assembly for the second end of the sleeve within the hull comprises a cap secured to the end of the sleeve, for example by a thread. The cap holds one or more seals to prevent the ingress of water. The cap may comprise a transparent portion or, alternatively, may hold a transparent plug in place at or over the end of the sleeve.

In a further embodiment, the wear indicator comprises a light sensing means, located to be exposed to light through wear of the anode or to detect light entering the cavity in the sacrificial anode. The light sensing means may comprise any suitable optically sensitive device that can provide an indication when it is exposed to light, for example when light enters the anode cavity. One suitable light sensing means is a photovoltaic device, operable to generate an electrical current when irradiated with light. The light sensing means may be connected, by a conventional electric circuit, to provide a warning indication or alarm at a suitable control panel, for example on the bridge of the vessel.

In one embodiment, the light sensing means is disposed with a sleeve having a bore therethrough, as hereinbefore described. The sleeve extends through a bore or aperture in the hull of the vessel and connects with the anode or the cavity in the anode, such that, as a result of corrosion of the anode, light impinging directly on the

end of the sleeve or entering the cavity in the anode passes into the bore of the sleeve and impinges on the light sensing means. Again, suitable seals are provided to render the sleeve assembly watertight to prevent the ingress of water into the hull.

The light sensing means may be used as an alternative to or in addition to the aforementioned arrangement allowing for a direct visual inspection of the wear indicator within the hull of the vessel.

When a light sensing means is employed, it is preferable to provide a means for testing the light sensing components and related circuitry. The test facility is provided by having a light emitting means disposed to direct light onto the light sensing means at any stage in the wear of the anode. This may be achieved, for example, by providing a light emitting means within the cavity of the anode or in association with the cavity, such as in the sleeve housing the light sensing means, whereby the entry of light into the cavity of the anode and its passage to the light sensing means may be simulated. Suitable light emitting means are known in the art and include light emitting diodes (LEDs). In one embodiment, the light emitting means are located within the sleeve housing the light sensing means and is operable to generate light within the bore of the sleeve, in similar manner to light entering the sleeve from the exterior or the cavity in the anode.

The sacrificial anode may be provided with a single cavity and an associated wear indicator. Alternatively, the anode may comprise a plurality of cavities, one or more of which may have wear indicators associated therewith. The use of a plurality of cavities can provide an indication of the wear at different locations in the anode. The cavities may extend at different depths, so as to provide an indication of the rate of wear of the anode. The cavities extending closest to the surface of the anode will be exposed to light earliest in the operational life of the anode, while those cavities furthest from the surface of the anode will generally take longer to be exposed to ambient light.

As described hereinbefore, the anode is preferably provided with a cavity that becomes open to the surroundings upon a predetermined level of wear of the anode

being reached. The cavity may be of any suitable size and depth. It will be appreciated that the closer the cavity extends to the surface of the anode when new, the less wear of the anode will take place before light enters the cavity and an indication of wear is provided by the present invention. Conversely, the further the cavity is from the surface of the anode, the greater the wear of the anode that can take place before a wear indication is provided. It will thus be appreciated that the wear indicator and method of the present invention may be employed without providing the anode with a cavity. Rather, a conventional anode is merely mounted over the wear indicator, for example over the bore or aperture in the hull of the vessel. Activation of the wear indicator, for example by light becoming visible through the bore or aperture in the hull, will only occur when the anode has been significantly or entirely corroded. Such an arrangement is within the scope of the present invention and the term 'cavity' is to be construed accordingly to include the aforementioned arrangement in which light reaches the wear indicator only when the anode has been completely lost to corrosion. However, it is to be understood that in such an embodiment the present invention will provide no indication of wear in advance of the complete loss of the anode, allowing the vessel to be unprotected for a period of time.

It will further be appreciated that the present invention is particularly advantageous in that it will provide an immediate indication of the loss of the anode, for example in cases where the anode becomes detached from the hull of the vessel or is inadvertently removed. It is a particular advantage of the present invention that the assembly may be arranged to be entirely independent of the anode, such that when the anode is damaged or removed, for example by a collision between the vessel and a submerged object, the wear indicator assembly remains undamaged and can indicate the loss of or damage to the anode.

In a further aspect, the present invention provides a sacrificial anode for use with a wear indicator assembly as hereinbefore described. In particular, the anode preferably has a cavity capable of being aligned in communication with a bore or aperture in the hull of the vessel and in which the wear indicator of the present invention is mounted.

In addition to the aforementioned apparatus and methods, the present invention provides a further arrangement of a sacrificial anode, in particular a sacrificial anode for use with ships, boats and the like. Accordingly, in a further aspect, the present invention provides a sacrificial anode assembly comprising a sacrificial anode for mounting to the surface of a component to be protected and an indicator member, the indicator member arranged to extend between the sacrificial anode and the surface of the component to be protected when the assembly is in place, the indicator member being of a size relative to the sacrificial anode that a portion of the indicator member is revealed when a predetermined level of corrosion of the sacrificial anode has occurred.

The assembly of this aspect of the present invention represents as very simple and robust means for indicating the extent of wear of a sacrificial anode. The assembly may use anodes of known and currently available configuration, with the indicator member being sized accordingly.

The indicator member may be of any suitable size and shape. One preferred arrangement is to have the indicator member in the form of a flat plate, extending between the anode and the surface of the component to which it is affixed. The plate may be any suitable shape, for example to match the outline and shape of the anode being used. In one embodiment, the indicator member is a disc.

The indicator member is preferably smaller in surface area than the surface of the portion of the anode adjacent the component to be protected. In this way, when the assembly is first installed, the indicator member is not visible. As the anode wears in the normal manner, the area of the component covered by the anode is reduced. At a given level of wear or corrosion, the anode is of sufficiently reduced size as to expose the outer portions of the indicator member. By being visible, the indicator member provides an indication of the level of wear of the anode, which can be used to determine whether replacement of the anode is required. As will be appreciated, the indicator member may be varied in size, according to the degree of

wear of the anode that is considered acceptable before the indicator member becomes visible and indicates that wear has occurred.

An assembly may comprise a kit of parts, including a sacrificial anode and a plurality of indicator members, each indicator member being of a size relative to the anode as to indicate a specific level of wear. In this way, the assembly may be adapted to different wear levels as may be applicable to different components to be protected.

The indicator member is preferably formed to have a bright colour, in particular a colour that is in contrast to the colour of the anode and the surface of the component to be protected, so that the indicator member is readily visible when exposed. The indicator member is formed from a wear and corrosion resistant material. Any suitable material may be used, with plastic being a most convenient material.

In one arrangement, the indicator member is provided with indicator means on its surface, which when exposed due to the wear of the anode, provide the viewer with an indication of the level of wear. For example, the indicator member may be provided with portions of different colours, for example concentric bands of different colours, each colour then corresponding to a predetermined degree of wear of the anode. As the anode wears, the various portions are progressively exposed, giving an indication of the degree of wear.

Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying figures, in which:

Figure 1 is a cross sectional view of a wear indicator and sacrificial anode assembly according to a first embodiment in place in the hull of a vessel;

Figure 2 is a cross sectional view of a wear indicator and sacrificial anode assembly according to a second embodiment in place in the hull of a vessel, with the anode in a new or substantially unworn state;

Figure 3 is a cross sectional view of the assembly of Figure 2, with the anode in a state of considerable wear;

Figure 4 is a cross sectional view of a wear indicator and sacrificial anode assembly according to a further embodiment of the present invention;

Figure 5 is a cross sectional view of the assembly of Figure 4 with a test device included; and

Figure 6a is a cross sectional view of an anode assembly of a further embodiment of the present invention with the anode in an unworn condition; and

Figure 6b is a cross sectional view of the anode assembly of Figure 6a with the anode in a worn condition.

Referring to Figure 1 , there is shown a sacrificial anode and wear indicator assembly, generally indicated as 2. The assembly 2 is in place in the hull 4 of a vessel, such as a ship, boat or yacht. A generally hemispherical sacrificial anode 6 is mounted to the exterior of the hull by conventional means (not shown for clarity). The anode 6 is provided with a cavity formed as a blind bore 8 extending from the surface of the anode adjacent the hull 4. A bore 10 extends through the hull 4. The bore 10 is aligned with the blind bore 8 in the anode 6. A plug 12 of transparent material, such as Perspex®, is mounted in the bore 10. The plug 12 has a flange 14 at its end adjacent the anode 6. A locking nut 16 is threaded onto the portion of the plug 12 within the hull and secures the plug 12 in the bore 10.

In use, as the anode 6 corrodes in normal manner, the surface of the anode approaches the blind bore 8. As the blind bore 8 becomes exposed, light, in

particular daylight, will enter the bore 8 and will be visible through the plug 12 from within the hull 4. This will provide an indication of the state of the anode and its level of wear. Should the anode 6 become detached and be lost, light will become immediately visible through the plug 12, indicating that action is required.

Referring to Figure 2, there is shown an alternative sacrificial anode and wear indicator assembly, generally indicated as 102. The assembly 102 is shown installed on the hull 104 of a sea going vessel. A sacrificial anode 106, of generally hemispherical configuration, is mounted to the exterior of the hull 104 by conventional means (not shown for clarity). The anode 106 comprises a cavity in the form of a blind bore 108 extending from the surface of the anode 106 adjacent the hull 104.

A wear indicator assembly, generally indicated as 110, is shown mounted in a bore 112 formed in the hull 104. The wear indicator assembly 110 comprises a generally cylindrical sleeve 114 having a longitudinal bore 116 therethrough. A flange 118 is formed at one end of the sleeve 114 and is in contact with the outer surface of the hull 104. A locking nut 120 is threaded onto the outer surface of the sleeve 114 and secures the sleeve against the inner surface of the hull 104.

At its inner end, the sleeve 114 is provided with a cap assembly 122 comprising a cap 124 threaded onto the free end of the sleeve. The cap 124 comprises a flange 126 extending around an opening 128 in its end portion. The flange 126 retains a transparent plug 130 on the end of the sleeve 114. Ring seals 132 and 134 are disposed between the plug 130 and the end of the sleeve 114 and the flange 126 of the cap, respectively. In an alternative arrangement to the one shown in Figure 2, the plug 130 extends into the sleeve 114 and the seals 132 and 134 are disposed between the plug and the inner surface of the sleeve 114. This arrangement may be preferred as the removal of the cap 124 from the sleeve 114 does not release the plug 130, which stays within the bore of the sleeve until removed.

The cap 124 may be provided with a locking screw (not shown for clarity), which bears against the sleeve 114 and prevents the cap from inadvertently becoming unscrewed from the end of the sleeve.

The assembly is shown in Figure 2 in the new or partially worn condition, that is with the blind bore 108 extending into the anode 106, with its innermost end being some distance from the outer surface of the anode. In this condition, no light incident on the anode 106 can enter the blind bore 108 and the sleeve 114. As shown in Figure 3, the anode 106 has undergone significant wear to such a degree that the inner most end of the bore 108 has become exposed to light that is incident on the anode, indicated by arrows 140. The light 140 passes along the bore 116 of the sleeve 114 and is visible through the transparent plug 130 of the cap assembly 122 to a person within the hull of the vessel. Thus, the worn condition of the anode is clearly indicated to the user.

It will be appreciated that the assemblies shown in Figures 1 , 2 and 3 are both very simple in construction and do not rely for operation on any electrical and/or mechanical systems or components. This in turn renders the assemblies particularly robust and reliable.

Referring to Figure 4, there is shown a further alternative sacrificial anode and wear indicator assembly, generally indicated as 202. The assembly 202 is generally of a similar construction that that shown in Figures 2 and 3 and is shown installed on the hull 204 of a sea going vessel. A sacrificial anode 206, of generally hemispherical configuration, is mounted to the exterior of the hull 204 by conventional means (not shown for clarity). The anode 206 comprises a cavity in the form of a blind bore 208 extending from the surface of the anode 206 adjacent the hull 204.

A wear indicator assembly, generally indicated as 210, is shown mounted in a bore 212 formed in the hull 204. The wear indicator assembly 210 comprises a generally cylindrical sleeve 214 having a longitudinal bore 216 therethrough. A flange 218 is formed at one end of the sleeve 214 and is in contact with the outer

surface of the hull 204. A locking nut 220 is threaded onto the outer surface of the sleeve 214 and secures the sleeve against the inner surface of the hull 204.

At its inner end, the sleeve 214 is provided with a cap assembly 222 comprising a cap 224 threaded onto the free end of the sleeve. The cap 224 comprises a cap end 226 having an aperture 228 therethrough aligned with a watertight cable clamp assembly 230. A generally cylindrical chamber 232 of transparent material extends within the bore 216 of the sleeve 214 and is held in place by means of a flange 234 retained between the end of the sleeve 214 and the cap end 226. Seals 236 and 238 are retained between the flange 234 of the chamber 232 and the end of the sleeve 214 and the cap end 226, respectively. In an alternative arrangement, the chamber 232 extends within the sleeve 214, as shown in Figure 2, and is provided with one or more seals between the outer surface of the chamber and the inner surface of the sleeve

A cable 240 extends through the cable clamp 226 and the aperture 228 in the cap end 226 into the chamber 232. The cable 240 is connected to the terminals of a photovoltaic sensor 242.

The wear indicator assembly 210 operates when ambient light is caused to enter the blind bore 208 of the anode 206 due to wear or corrosion of the anode (as shown in Figure 3 and described above). Light entering the bore 208 and the bore 216 of the sleeve 214 impinges on the sensor 242, which generates a signal in the cable 240. The signal is used to provide an indication or alarm at a suitable control panel (not shown for clarity), such as in the bridge of the vessel.

Referring to Figure 5, there is shown a sacrificial anode and wear indicator assembly of substantially the same construction as that shown in Figure 4 and described hereinbefore. Components in Figure 5 of the same configuration as those of Figure 4 are indicated using the same reference numerals.

The assembly of Figure 5 further comprises a test assembly, generally indicated as 250 and comprising a light emitting diode (LED) array 252 disposed

within the bore 216 of the sleeve 214 and connected to a control panel (not shown for clarity) by a cable 254. Activation of the LED array 252 causes light to be emitted and impinge on the sensor 242, in turn causing the indication or alarm to be activated. In this way, the integrity of the wear indicator system may be checked at any point in the operational life of the anode.

Referring to Figure 6a, there is shown a sacrificial anode assembly, generally indicated as 302, mounted to the exterior surface of a component 304 to be protected from corrosion and wear. The assembly 302 comprises a sacrificial anode 306 of conventional configuration generally in the form of a dome. The sacrificial anode 306 is mounted to the component 304 by means of a bolt 308 extending through a bore in the anode and through a corresponding bore in the component 304. A nut 310 secures the anode, in conventional manner. An indicator member 312 is disposed between the anode 306 and the exterior surface of the component 304. The indicator member 312 is in the form of a disc of brightly coloured plastic. The anode 306 is connected electrically to the component 304 by means .of the bolt 308.

As will be noted from Figure 6a, the indicator member 312 is smaller in area than the portion of the anode adjacent the component 304, such that when newly installed, as shown in Figure 6a, the indicator member is not generally visible to a viewer from the exterior of the component.

Referring to Figure 6b, the assembly 302 of Figure 6a is shown with the anode 306 having experienced substantial corrosion and wear. As shown, the extent of wear of the anode is such that the body of the anode 306 has significantly decreased in size. In particular, the anode 306 has reduced in size so as to uncover the radially outer portion of the indicator member 312, which is now clearly visible to a viewer. Once the indicator member 312 becomes visible, the viewer is provided with an indication of the extent of the wear of the anode and can make an assessment regarding replacing the anode to ensure continued protection for the component 304.

As will be appreciated, the selection of an indicator member 312 having a larger diameter than shown in Figures 6a and 6b would provide an earlier indication of wear of the anode 306. Conversely, an indicator member 312 of smaller diameter would require further corrosion of the anode 306 to take place, before becoming visible to a viewer.