GB2427877A

GB2427877A - Corrosion protection system

Info

Publication number: GB2427877A
Application number: GB0612983A
Authority: GB
Inventors: Roddy James
Original assignee: IICORR Ltd
Current assignee: IICORR Ltd
Priority date: 2005-06-30
Filing date: 2006-06-30
Publication date: 2007-01-10
Also published as: GB0513344D0; GB0612983D0

Abstract

A corrosion protection system 1 for protecting a metal object W against corrosion comprises a sacrificial anode 20 and a bracket 2 to connect the anode 20 to the object W. The anode 20 and the bracket 2 are adapted to connect together in a cantilever arrangement. Preferably, the anode 20 has two ends and the bracket 2 can be adapted to connect to the anode 20 at one end and the other end of the anode 20 can be unrestrained in a cantilever arrangement. The anode 20 can be pivotally mounted relative to the bracket 2 such that the anode 20 is moveable relative to the object W. The system 1 may be used on a submerged metal object W, rendering unnecessary the underwater welding steps required in conventional systems and simplifying the installation method. A method of protecting a metallic submerged object W against corrosion is also disclosed, including forming an electrical connection between the anode 20 and the object W being protected.

Description

"Corrosion Protection System" This invention relates to a corrosion

protection system, particularly adapted for use in the protection of underwater metallic objects, such as metal sheet walls used in the fabrication of piers and other marine structures. Such metal sheet walls are examples of piles, and the invention is particularly suited to use with all types of marine piling.

Cathodic protection is a well-known countermeasure for combating corrosion in submerged metal objects. Most cathodic protection systems are sacrificial anode arrangements comprising a metal anode bolted, welded or otherwise attached to the metal object to be protected. The anode is made from a metal that is dissimilar to the metal being protected, and sacrificially corrodes in preference to the protected metal object. ....* U...

These sacrificial anodes typically comprise elongate structures of the * sacrificial metal that are attached at each end to brackets, which are attached to the metallic object being protected. The anode is typically welded to the brackets, which are welded to the pile, in order to ensure a good electrical connection between the anode and the cathodic pile. S...

Only the portion of the anode that is submerged in the electrolyte will ** function as an electron donor to protect the cathodic metal object, and so it is commonplace to install the anode well below the height of the lowest astronomical tide, or LAT position, so that the anode is always submerged and available to protect the metal object with maximum efficiency.

However, this leads to difficulties in the installation process, because at least four underwater welding actions are necessary to connect the anode in place at the top and the bottom.

According to the present invention there is provided a corrosion protection system for protecting a metal object, the system comprising a sacrificial anode and a bracket to connect the sacrificial anode to the object being protected, wherein the anode and the bracket are adapted to connect together in a cantilever arrangement.

Typically a single bracket is used in the system.

Typically the anode has a generally elongate structure. The bracket is adapted to connect to the anode at one end of the anode, and the opposite end of the anode is typically unrestrained in a cantilever arrangement. In certain embodiments of the invention, the anode can pivot relative to the bracket during the installation, so that the anode can be manoeuvred into position relative to the object without under-water, S *S.I welding activities being required. Typically the anode and bracket are connected together in a cantilever manner at one end of the anode once the bracket is installed on the object, and then the anode is then moved pivotally relative to the bracket and the object to assume its in use position. * S. .

Typically the bracket is installed above the mean low water mark for spring tides (sometimes called the MLWS point) and is advantageously installed above the lowest astronomical tide (or LAT) point on the metal object.

The anode typically comprises a sacrificial metal adapted to corrode preferentially relative to the metal object to which it is connected. The metal of the anode can be selected in accordance with the particular situation, but is typically dissimilar to the metal being protected, and typical materials of conventional aluminium, zinc and indium alloy anodes are quite suitable for this purpose.

Typically the anode has a sacrificial portion and an attachment portion.

The sacrificial portion typically comprises the dissimilar metal and the connector portion typically comprises a connector bar that structurally connects the sacrificial portion to the bracket. The connector bar can simply be plain steel, and typically spaces the attachment portion of the anode away from the sacrificial portion, so that the sacrificial portion can be completely submerged in use, while the attachment portion extends out of the water to physically connect the anode to the bracket. In some embodiments, the anode can be formed of a continuous length of steel bar forming a core of the anode throughout its length, with the sacrificial portion cast in place around in the bar. The lower end of the bar can form a crank that spaces the sacrificial portion at the optimum distance from the object. The upper end of the bar can form the attachment portion with a further crook, a T-piece or with some other attachment means.

In typical embodiments, the bracket can be installed at low tide by directly welding the bracket onto the object without any submerged welding operations being required. After the bracket has been welded in place, the *SSS attachment portion of the anode can then be engaged with the bracket, and the anode can then be pivotally lowered into position so that the sacrificial portion of the anode is submerged, optionally below the low water mark, and preferably below the LAT point, thereby increasing the chance of the sacrificial portion of the anode being submerged during every part of the tidal cycle. It is advantageous that the bracket is welded to the object being protected since this creates a stable electrical connection, but any kind of physical attachment that creates an electrical connection between the object and anode is suitable. Likewise, the anode is typically welded to the bracket to complete the electrical connection, but any physical connection that completes the electrical connection between the anode and the object is suitable. Bolts and screws are examples of suitable fixing means to complete the connection in this regard. Typically the weld or bolt that connects the anode to the bracket is only required to complete the electrical connection in the circuit, and does not necessarily need to be a structural weld or bolt capable of bearing the full weight of the anode. For this purpose, the bracket typically comprises a structural connector such as a hook portion that engages with the attachment portion of the anode and which optionally permits pivotal movement of the anode relative to the bracket while the attachment portion is engaged in the hook.

Omitting the electrical and physical connections at the lower end of the anode renders unnecessary the underwater welding steps required in conventional systems, and simplifies the installation method.

The invention also provides a method of protecting a metallic submerged object against corrosion, the method comprising connecting a bracket to the object, connecting an anode to the bracket, thereby forming an electrical connection between the anode and the object being protected, S. .

and wherein the anode is connected to the bracket in a cantilever arrangement.

The connections can be by welding, bolting or by some other means.

The invention also provides a corrosion protection system for protecting a metal object, the system comprising a sacrificial anode and a bracket to connect the sacrificial anode to the object being protected, wherein the anode is connected to the object by a single bracket.

Embodiments of the present invention will now be described by way of example, and with reference to the accompanying drawings, in which: Fig. 1 is a side view of a corrosion protection system installed on a sheet piled wall of a pier; Fig. 2 is a plan view of the Fig. 1 system.

Fig. 3 is a plan view of a bracket of the Fig. 1 system; Fig. 4 is a front view of the Fig. 3 bracket; Fig. 5 is a side view of the Fig. 2 bracket; Fig. 6 is a side view of a second bracket for use with the Fig. 1 system; Fig. 7 is a front view of an anode of the Fig. 1 system; Fig. 8 is a side view of a further embodiment of a protection system; Fig. 9 is a plan view of the Fig. 8 system; Fig. lOis a plan view of a bracket of the Fig. 8 system; Fig. 11 is a front view of the Fig. 10 bracket; and Fig. 12 is a side view of the Fig. 10 bracket. :..

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Referring now to the drawings, Figs. 1 and 2 show a sheet piled wall W of S..

a conventional design, having a corrugated surface with recesses commonly known as inpans I that extend inwards from the outer surface of the wall W. An example of a corrosion protection system that is protecting the wall from corrosion by cathodic protection is shown in Fig. 2 mounted on one inpan I on the wall W. The system 1 comprises a bracket 2 welded to the inpan, and an anode hooked and welded to the bracket 2.

The bracket 2 is formed from mild steel and typically comprises a body 5 consisting of a length of generally C-shaped channel section, having on its central web a pair of hooks 10 and a pair of stabilisers 15. The hooks 10 can be simple lengths of C-shaped channel section with one leg attached to the central web of the body 5, so that the C-shaped channel of the hooks 10 point upwards. The stabilisers 15 can simply be sections of Lshaped angle iron attached to the body 5 below the hooks, so that one leg of each stabiliser extends outwards from the central web of the body 5.

The hooks 10 and stabilisers 15 in each pair are spaced laterally from one another by a set distance, in this case 80mm, and are aligned with one another, so that the gap between the hooks 10 lines up with the gap between the stabilisers 15. As shown in dotted lines in Fig. 5, the hooks can have either a straight outer leg lOs or a canted outer leg lOc, which can help to secure the anode against removal, as described below.

The hooks 10 and stabilisers 15 are typically welded to the body 5, which **..

is welded to the wall W using a fillet weld. .:: Fig. 6 shows a different embodiment of a bracket 2' having a body 5' as before, but instead of the hooks and stabilisers an attachment plate 11' is welded to the central web of the body 5'. The attachment plate has a chamfered upper surrace 1 lu' above a pair of hooks 10', which are integrally formed with the plate 11'. Below the hooks 10', a pair of stabilisers can be welded in place or integrally formed with the plate 11'.

The integral formation of the hooks and the stabilisers with the attachment plate means that the alignment of the components of the bracket can be set in a factory rather than on-site, and can therefore be more consistent than if they are separately welded direct to the body 5.

The anode 20 comprises a mild steel bar 22 having a straight upper end 22u with a T shaped connector 24, and a crooked lower end 221 having a Tshaped stabiliser 26. The crooked lower end, as shown in Fig. 1, bends through 900 so that the lower end 221 is perpendicular to the upper portion 22u. The T-shaped connector 24 and stabiliser 26 each have arms 24a, 26a that extend laterally perpendicular to the bar 22.

The anode 20 has a sacrificial portion 28 connected to the bar 22, which forms a core extending from one end of the sacrificial portion 28 to the other. The sacrificial portion 28 is cast or otherwise attached to the core of the bar 22, and comprises conventional sacrificial metal alloys such as aluminium, zinc and indium among other elements. The sacrificial portion 28 is typically electrically coupled to the bar 22 by means of the casting process.

The anode has an attachment portion at its upper end comprising the upper part of the bar 22u and the T-shaped connector 24. * ***

I.., S * * * S When the anode is to be installed, the bracket is first welded or otherwise attached to the wall W at a height on the wall W that is calculated on a case by case basis to be above the LAT point, and preferably above the MLWS point, so that the bracket can be welded to the wall W without any S...

complex underwater welding steps. In addition to spacing the bracket above the LAT and MLWS points, the height of the bracket on the wall W is chosen with reference to the length of the upper portion 22u of the bar 22, so that the upper end 28u of the sacrificial portion 28 will be below the MLWS point, and preferably below the LAT point, when the anode is installed.

In the example shown in Fig. 1, the bracket 2 is installed 2.5m above the LAT point, and the length of the upper portion 22u of the bar 22 is such that the upper portion 28u of the sacrificial portion 28 is just below the LAT point. Hence the position of the bracket is chosen so that the bracket can be welded to the wall W above the water line at the time of installation (usually at low tide), and so that the sacrificial portion 28 of the anode 20 will always be submerged during every point of the tidal cycle.

The installation can be carried out from the deck D, or from a platform lowered from the deck in the case of an adverse overhang, as is shown in Fig. 1.

After the bracket 2 has been welded or bolted to the wall W at the desired height above the LAT point, the T-shaped connector 24 on the connector portion of the anode is offered to the open end of the hooks 10. In some embodiments, the anode is installed from the deck D above the bracket, by upending the anode and lowering it upside down so that the T- shaped connector 24 is lowermost, and is the first part of the anode to engage the **.

upwardly extending open ends of the hooks 10. When the hooks 10 have engaged the T-shaped connector 24 and the upper portion of the bar 22u is located between the hooksl 0, the anode can be pivotally moved around * the axis of the T-shaped connector to move the lower end 221 down towards the wall W. Chamfered edges on the body 5 assist with the **** capture of the T-shaped connector 24 by the hooks 10. *:::: The anode 20 is allowed to pivot in this manner until the upper portion 22u of the bar engages with the stabilisers 15 welded to the bracket 2 below the hooks 10, which receive the bar 22 between them and prevent any lateral movement of the bar 22 (and thus of the anode) relative to the bracket 2. At that point, the bar 22 is pressed against the central web of the body 5 (or against the attachment plate 11') and can be tack welded in position along the length of the stabilisers 15. The tack weld helps to prevent relative movement, and ensures the electrical connection between the anode 20 and the bracket 2.

The anode 20 is typically spaced away from the wall by the depth of the bracket 2 and by the dimensions of the crook at the lower portion 221 of the bar, each of which are chosen in each circumstance to space the anode 20 at the optimum distance from the wall W. In the example shown in Fig. 1, the anode is spaced around 200-300mm from the inner surface of the inpan I. The length of the arms in the T-shaped connector 24 and the stabiliser 26 are chosen to match the width of the inner surface of the inpan, so that when the anode 20 is in position as shown in Fig 1, the ends of the arms on the connector 24 and stabiliser 26 abut the sides of the inpan and restrain lateral movement at the top and bottom of the anode 20, relative to the bracket 2. S * *

The connection of the anode 20 through the bracket 2, 2' is sufficient to complete an electrical circuit when the anode is submerged in the seawater, so the anode protects the wall W against corrosion. However, since there is only one bracket needed to install the anode, and since it can be installed without the requirement of underwater welding, the installation of the anode is simplified, as is its retrieval for maintenance and inspection operations after installation.

Referring now to Figs. 8-12, a further embodiment of the invention has an anode 20 as previously described and a modified bracket 2". The bracket 2" has a body 5" with a sloped upper face 5"u (assisting with capture of the arms 24a of the T-shaped connector). At the lower end of the upper face 5"u two hooks 10" are welded to the body 5", each comprising C- or Ushaped channel sections of mild steel similar to the hooks 10 of the first embodiment. The hooks 10" are welded in place above a single C- shaped channel stabiliser 15", also welded to the central web of the body 5", and having a gap between the arms of the channel that is identical to the gap between the hooks 10". The gaps are vertically aligned with one another, and are intended to receive the upper portion 22u of the anode 20 as previously described. In fact, the hooks 10" and the stabiliser 15" can be made from separate cuts of the same C-shaped channel section to save on materials and welding.

In this embodiment, the hooks 10" each have at least one aperture lOa drilled through their outer flanges, to receive a bolt(not shown) securing the arms 24a of the T-shaped connector 24 of the anode 20. The aperture can be threaded to receive the bolt or can have a threaded nut (not shown) welded to the outer face of the flange at the aperture iCa. The aperture is typically at a location chosen with respect to the dimensions of the arms 24a of the T-shaped connector 24, so that the bolt either passes over the top of the arms 24a when they are received in the hook 10", or impacts against the upper surface of the arms 24a to prevent, in either case, the removal of the connector 24 from the hooks 10" after the bolts: ,.

have been tightened.

Likewise, the stabiliser can have an aperture 15a that is threaded or plain, . : to receive another bolt (not shown) to restrain the bar 22 within the channel of the stabiliser 15".

In addition to the physical connection, the bolts also ensure the electrical connection between the anode 20 and the bracket 2".

Thus in the present embodiment, the anode 20 can be secured in place by bolting instead of, or in addition to, welding operations.

If desired, the bracket 2" can be bolted, instead of welded, to the wall W. Modifications and improvements can be incorporated without departing from the scope of the invention. **.s * * * *** * * S * *

S * S. * * S *** j * S S... * S.. * S S &. S

Claims

1. A corrosion protection system for protecting a metal object, the system comprising a sacrificial anode and a bracket to connect the sacrificial anode to the object being protected, wherein the anode and the bracket are adapted to connect together in a cantilever arrangement.

2. A corrosion protection system as claimed in claim 1, wherein the anode has two ends and the bracket is adapted to connect to the anode at one end and the other end of the anode is unrestrained in a cantilever arrangement.

3. A corrosion protection system as claimed in any preceding claim, wherein the anode is pivotally mounted relative to the bracket such that the anode is moveable relative to the object. .. 4.

4. A corrosion protection system as claimed in any preceding claim, ., wherein the anode has a sacrificial portion and an attachment portion, : . ., wherein the sacrificial portion comprises a sacrificial metal adapted to corrode preferentially relative to the object to which it is connected and the attachment portion comprises a connector bar that structurally connects..

the sacrificial portion to the bracket.

5. A corrosion protection system as claimed in claim 4, wherein the connector bar is manufactured from steel.

6. A corrosion protection system as claimed in claim 4 or claim 5, wherein the connector bar spaces the object away from the sacrificial portion.

7. A corrosion protection system as claimed in any of claims 4 to 6, wherein a lower end of the connector bar is formed as a crank that spaces the sacrificial portion at an optimum distance from the object.

8. A corrosion protection system as claimed in any of claims 4 to 6, wherein an upper end of the connector bar is formed as an attachment means for engaging with the bracket.

9. A corrosion protection system as claimed in any of claims 4 to 8, wherein the connector bar forms a core of the anode. * S.. * S

10. A corrosion protection system as claimed in claim 9, wherein the sacrificial portion is cast around the connector bar. : :.

11. A corrosion protection system as claimed in any of claims 4 to 10, *.

wherein the bracket comprises a connector that engages with the *.

attachment portion of the anode.

12. A corrosion protection system as claimed in claim 11, wherein the connector permits pivotal movement of the anode relative to the bracket when the attachment portion is engaged with the connector.

13. A corrosion protection system as claimed in claim 11 or claim 12, wherein the connector comprises a hook portion.

14. A method of protecting a metallic submerged object against corrosion, the method comprising connecting a bracket to the object, connecting an anode to the bracket thereby forming an electrical connection between the anode and the object being protected, and wherein the anode is connected to the bracket in a cantilever arrangement.

15. A method as claimed in claim 14, including welding the bracket to the object being protected.

16. A method as claimed in claim 14 or claim 15, including welding the anode to the bracket to electrically connect the anode and the object being protected.

17. A method as claimed in any of claims 14 to 16, including installing * .S* the bracket on the object, pivotally connecting one end of the anode to the * * : bracket in a cantilever arrangement and moving the anode relative to the bracket and the object to assume its in use position. :

18. A method as claimed in any of claims 14 to 17, including installing **** the bracket on the object above the mean low water mark for spring tides.

19. A method as claimed in any of claims 14 to 18, including installing the bracket on the object above the lowest astronomical tide point.

20. A method as claimed in any of claims 14 to 19, including installing the bracket to the object at low tide by welding the bracket onto the object.

21. A method as claimed in any of claims 14 to 20, including engaging the anode with the bracket, following welding of the bracket to the object.

22. A method as claimed in claim 21, including pivotally lowering the anode into position so that a sacrificial portion of the anode is submerged in water.

23. A corrosion protection system for protecting a metal object, the system comprising a sacrificial anode and a bracket to connect the sacrificial anode to the object being protected, wherein the anode is connected to the object by a single bracket and has no further structural connections between the anode and the object. * S **.* * ..S * S S * * *S. * * *S * S * ***. * S *.*S S...

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