Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B59/00—Hull protection specially adapted for vessels; Cleaning devices specially adapted for vessels
  • B63B59/04—Preventing hull fouling
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/04—Controlling or regulating desired parameters
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B2221/00—Methods and means for joining members or elements
  • B63B2221/10—Methods and means for joining members or elements using adhesives
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B2231/00—Material used for some parts or elements, or for particular purposes
  • B63B2231/02—Metallic materials
  • B63B2231/12—Copper or copper alloys
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F2213/00—Aspects of inhibiting corrosion of metals by anodic or cathodic protection
  • C23F2213/30—Anodic or cathodic protection specially adapted for a specific object
  • C23F2213/31—Immersed structures, e.g. submarine structures

Definitions

• the rate of leaching is not constant.
• the layer exposed to the water is first exhausted, later followed by deeper laying layers.
• the antifouling paints becomes less and less effective with exposure time. This is particularly true for pleasure boats, many of which spend most of their time at rest at their moorings. Hence the antifouling is subdued to little attrition and the active antifouling components have to diffuse through the paint layer to reach the water.
• the paint matrix is frequently made of components permitting the release of the toxic substance when in contact with water.
• the matrix thus assumes an open structure actually absorbing the water and some types, so called self polishing, dissolves slowly I water.
• This inevitable and necessary property of constituting an open structure strongly reduces the paints protective qualities in all other respects than its antifouling properties.
• paints offer no protection against so-called "osmosis", the uptake of water by the polyester laminate, frequently being the preferred material for boat construction.
• the antifouling paints equally, offers no or very poor additional protection of the hull against mechanical chocks.
• antifouling paints because of its open structure, are mat, giving the underwater surface a rough finish. This roughness, which is in the order of 250 microns, adds significantly to the water resistance and the cost of propelling the vessels.
• a further inconvenience with antifouling paints is its property to smear on contact. Whilst the boat in water, any contact with the antifouling paint will cause smearing of the object with the paint leaving patches that are difficult to remove. Many have had their ropes, fenders and bathing suits destroyed by contact with antifouling paint.
• hulls were made of wood.
• the underwater parts were protected by covering the hull beneath the water line by nailing sheets of copper by the use of copper nails to the wooden hull.
• the US patent US4987036 describes a method trying to overcome the problem of using copper-containing sheets to surfaces for their protection against fouling. Also this method necessitates the prior bonding of the copper-containing sheets to a supporting structure, made of a mesh, grid or an elastic material, for subsequent bonding of this laminate, using exclusively a curable neoprene rubber, to the surface to be protected. This method overcomes the problem of covering curved shapes by first bonding, to the above mentioned supporting structure, narrow copper or copper nickel sheets comprising a plurality of individual strips of copper or a copper-nickel alloy in the form of substantially parallelogram in shape.
• paints containing copper have been regulated in some countries. In Sweden for exempel, such paints are not allowed to release more than 200 micrograms of copper per cm2 during the first 14 days in contact with water as measured by a standardised analytical method. Also other countries have introduced such restrictions.
• An efficient antifouling thus only needs to act on the actual attachment phase by blocking these enzyme systems. Indeed the biochemical reactions leading to fouling takes place in the very vicinity of the surfaces, probably within a few microns. An antifouling thus has to be active only in this extremely thin layer thus blocking the adherence of the organisms to the hull.
• the present invention describes a method, a product and its application, permitting an effective and practical use of copper-containing conductive layers to counteract biological fouling on any surface including complicatedly shaped surfaces such as boat-or ship hulls in particular.
• the new method completely eliminates the detrimental effect on the environment normally resulting from antifouling active substances.
• the method offers a breakthrough in the way the antifouling effect can be controlled as the effect can be "switched” on and off in line with the need for antifouling.
• the copper-containing conductive layer may be constituted of plates, sheets, foils, grid or mesh or smaller pieces such as flakes of such applied so as to form a conductive layer.
• the method moreover overcomes the difficulties of bonding copper-containing sheets to surfaces, curved in three dimensions.
• the method also and additionally provides further protection of the underwater surfaces against damages caused by the surfaces contact with water such as so called osmosis and the method adds to the strength of the structure and its resistance to mechanical shock.
• the use of the method further reduces the roughness of the hulls thus permitting improved fuel economy or higher speeds.
• the protected surface moreover, becomes essentially smear-free thus offering enormous advantages both when it comes to handling of the protected surface and the almost total absence of environmental impact when cleaning.
• the method provides protection from fouling over a period of several years.
• cathodic protection can be achieved either by assuring a metallic contact between the metal to be protected and a so called sacrifice anode, made by a less noble metal, mostly zinc or aluminium, or by applying a source of electricity in the form of a direct current thus rendering the surface to be protected passivated or immunised.
• cathodic protection is nevertheless employed as it was surprisingly observed that removing the cathodic protection for short periods of time restored the antifouling effect without loosing any of the protection regarding corrosion.
• This particularly interesting aspect of the invention offers a completely unique and novel method to prevent fouling without any environmental impact whatsoever.
• Copper-containing materials are heavy and thick plates may not become sufficiently bonded to withstand its tendency to fall down by its own weight. Also this is avoided using very thin sheets or foils. Such thin sheets may basically be held in place by the hydrostatic pressure exerted on them by the water pressure, provided that essentially no water is permitted to enter between the surface to be protected and the copper-containing sheet itself. Such close contact can be achieved by the use of one or several commercially available adhesives.
• the copper-containing sheet must additionally have properties such as to permit its firm bonding to the surface to be sheeted. Also this is facilitated by the use of very thin and soft sheets.
• Copper-containing materials have a high thermal expansion coefficient, which differs much from that of the materials normally used for ship-and boat hulls.
• a thin and soft copper-containing sheet exerts less global strain on the bonding than a thick one as the temperature changes.
• the surface to be coated must also be prepared so as to enable its sheathing. Also this aspect is covered by the new invention.
• the sheathing must be reversible, i.e. some day, eventually, all hulls must be refurbished and the removal of the sheathing must not be virtually impossible, risk to destroy the hull itself or otherwise cause damage to it.
• One aspect of the new invention takes full account of this most important aspect.
• thin, soft copper-containing sheet or foil is bonded directly, without the need for supporting films or structures, to the curved surfaces to be protected by the use of any commercially available adhesive suitable for the water resistant bonding of copper-containing onto the surface to be protected. Because of the softness and the low weight of such thin copper-containing foils the strain on the bonding is low and the bonding itself, with the proper selection of adhesive, becomes stronger than the foil itself. The practical thickness of the foils was found to be in the range of 10 to 250 microns.
• thin copper-containing sheets or foils can be prepared in advance with a water-resistant adhesive, which can be activated at a later time when the actual sheathing is to take place.
• a water-resistant adhesive which can be activated at a later time when the actual sheathing is to take place.
• Such adhesives can be any of the types found among the group of "tapes", known under the commercial names as “Scotch”, “Tesa” etc. Such adhesives are frequently derivatives of acrylics but the invention is in no way limited to the use of such acrylics as any water-resistant adhesive can be used.
• the foils may thus be prepared in advance to form a composite tape where the adhesive side would be covered by a so-called release cover to be removed just prior to the sheathing. Also other suitable adhesives can be used as those activated by heat, solvents or other methods.
• thin copper-containing sheets can be used to constitute an integral part of a ship's or boat's hull.
• Boats made of glass fibre reinforced resins, like polyester, epoxy etc. are produced by laminating the fibreglass with the resin in moulds. When the laminate has hardened and cured, the mould is removed and the hull is then fitted with such further details as to make it complete. The bottom must then be painted with antifouling.
• the present invention facilitates the completion of the hulls.
• the copper-containing sheet is first placed on the part later of the mould later to hold the underwater part of the hull, then the laminating proceeds as usual, taking into full account to use a laminating resin having a sufficient adhesion to the copper-containing foil.
• the laminate has hardened and cured and the mould has been removed, the hull already has its underwater part sheathed with the copper-containing sheet. In this way the finished hull will have an incorporated antifouling treatment.
• the same technique can be used for any item, produced in moulds and which should possess antifouling properties
• the copper-containing sheets are mounted to the surface in such a way as not to expose any edge of copper-containing sheet to the main direction of the water flow. This may be achieved by ensuring to overlap the sheets "downstream" thus effectively reducing the risk of the sheets being peeled off by the action of the flow of water over the surface when the vessel is making headway.
• a breakthrough in antifouling technique is offered in the aspect of the invention where the antifouling effect can be controlled as to coincide with the need to prevent fouling.
• Copper metals in contact with natural water having slightly basic pH values may exist in three distinct states: At a low enough redox potential copper shows immunity and no corrosion occurs.
• copper can also be in a passive state which is also corrosion free but an oxidation to Cu2O or CuO occurs on the surface.
• full corrosion occurs at high redox potentials, low or high pH values and in the presence of anions like chloride. Copper is in this state released as Cu 2+ or CuO2 2- ions. Which state copper is in is thus a function of its redox potential. Copper in its immune state is inert and does not corrode which is favourable but on the other hand does not offer any antifouling properties either.
• the passive phase or state is antifouling active but a layer of copper oxides develops, grow thicker and the antifouling diminishes with time. This invention relates to alternating between these states.
• the transition from immune to passive and visa versa can be controlled.
• Such a controlled effect can be established by the connection of an sacrifice anode, made of a metal less noble than copper, to the copper containing sheet in such a way that said connection may be disconnected at intervals.
• the anode may be connected to the copper sheets by means of a circuit via a switch, which can be closed or opened. When the switch is open the anode is not electrically in contact with the copper-containing conductive layer or sheet and thus the copper is in an active phase as to what corrosion concerns. However, when the switch is closed, the anode is again connected to the copper sheet and the cathodic protection is restored.
• Said switch may be operated by a timer or other device so as to regulate the time intervals.
• the same effect can be achieved by mechanical means, making the anode alternating between being physically in contact with the copper sheet and not in contact.
• a third possibility is to use an applied current from a separate current source.
• This particularly effective method ensures that the copper containing sheathing remains antifouling-effective as no oxide layer develops and on the same time the copper surface is fully protected from corrosion.
• the timer was set to close the circuit for 45 minutes and disconnect the aluminium anode from the copper sheet for 15 minutes, this cycle repeating every hour.
• the copper sheet was weighed at intervals and the biological growth observed.
• a control piece of inert Teflon was covered by a thick layer of algae.
• Another control piece of copper foil without any cathodic protection was equally covered by a layer of algae.
• the table below shows the test results. Days Loss (Calculated as ⁇ m/year from start of test) 4 1.8 8 -6.7 14 -6.7 27 0.1 59 0.1
• copper-containing foil as thick as typically 100 micron of the soft quality, supplied by the company Outokompu, Viferas, Sweden could be shaped to follow any curvature present on boat hulls. This thickness would correspond to about ten years of heavy use, a considerable advantage compared to antifouling paint practice of repainting mostly every year.
• the roughness of the copper-containing foil was in the order of 5 microns.
• the surface to be protected was first prepared in the same way as in example 1 but using a glossy paint.
• the surface of the hull to be studied was first clad with the double-sided tape (so called adhesive transfer tape available from the company 3M) making sure to cover the entire underwater surface and a band some decimetres above the waterline.
• adhesive transfer tape available from the company 3M
• the copper-containing-containing foil was pressed firmly, against the adhesive tape by the aid of a rubber roller. Care was taken not to enclose any air under the copper-containing-containing foil. Thus the work proceeded until the entire surface, to be studied, was covered.
• glossy paint was used in this example, the invention is in no way limited to the use such paint as also mat paint gives satisfactory results.
• the boat was then launched.
• a hydrostatic pressure actually counteracted the weight of the copper-containing sheathing so that in theory no further bonding would be required under static conditions, which explains why such a relatively unqualified adhesive turned out to have sufficient bonding strength.
• a boat or ship does not stay at rest and the water swirling by, when the hull makes headway, exerts a force on the sheathing. To avoid “peeling" off of the sheathing, it was applied in such a way as to ensure that all overlapping of the sheets was done "downstream" i.e. the surface was clad from stern to bow.
• the copper-containing-containing sheet could be easily removed by heating the sheet by means of a hot air gun and a scraper.
• the surface to be sheeted was first prepared by proper cleaning, sanding and painting with a polyurethane paint.
• a copper-containing sheet 100 microns thick and from the same supplier, had been washed and treated to ensure the removal of grease and loose oxides. After drying, the double-sided transfer tape was applied to the copper-containing sheet, leaving the protective outer film intact.
• the protective film was then removed and the copper-containing sheet, with its transfer tape, was pressed against the surface of the boat hull by means of a rubber roller.
• the surface to be protected was prepared in the same way as in example 1, 2 and 3.
• the surface was then coated with a heat sensitive adhesive tape, available from 3M Company.
• a heat sensitive adhesive tape available from 3M Company.
• Such tapes perform like ordinary tapes but their bonding properties can be much improved on heating the substrate after the initial bonding.
• the copper-containing sheet was applied in the same way as in example 1 and 2 but the surface was later heated using an electrically heated "iron” device so as to cure the bonding according to 3M's specifications.
• a mould normally used for the production of boat structures, was first clad with the thin copper foil on the part to be under water in the finished hull. Then, on top of the copper foil, this area was laminated using epoxy resin and a thick glass fibre weave, commercially readily available.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Combustion & Propulsion (AREA)
• Ocean & Marine Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Laminated Bodies (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

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Cited By (4)

Citations (8)

• 2000
  • 2000-05-16 EP EP00440142A patent/EP1084947A1/fr not_active Withdrawn

Patent Citations (9)

Non-Patent Citations (1)

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