CA1075866A - Process for protecting the metal parts of a submarine electric cable against the action of corrosive agents and cable obtained thereby - Google Patents

Abstract

PROCESS FOR PROTECTING THE METAL PARTS OF A
SUBMARINE ELECTRIC CABLE AGAINST THE ACTION
OF CORROSIVE AGENTS AND CABLE OBTAINED THEREBY

ABSTRACT OF THE DISCLOSURE: An electric cable for sub-marina use which differs from prior art cables having a fluid impervious sheath in that-such sheath is the outer sheath and contains one or more compounds of heavy metals which chemically react with and neutralize corrosive fluids.
Also, processes for applying the sheath in which the heavy metal compound is mixed with an extrudable natural or synthetic polymeric material and the mixture is extruded over the usual cable parts, e.g., electrical conductor, insulation and armor, or in which a bituminous material admixed with a heavy metal compound is deposited in a channel element formed from an elastomeric material, the cable parts are laid in the mixture, the cable parts are covered by more of the mixture which is smoothed and the added mixture is covered by a further similar channel ele-ment which co-operates with the first channel element to form an outer envelope.

Description

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1 ~ The present invention relates to a process for

2 1. protecting a submarine electric cable against the corrosive I action exerted on the various metal parts of which it is 4 11 constituted, by fluids which may be present in the liquid l medium in which the cable is immersed and to a cable ob-6 ¦ tained by such process.
7 ~ The process of the invention is applicable to a

3 ¦ submarine electric cable, namely, one intended to carry 9 out electric connections and at least part of which passes o through water zones in which it is covered by water and 1 is, therefore, laid on sea or lake bottoms and the like.
12 The cable may have any conventional structure, and there-13 fore, the invention is applicable to a submarine electric cable whose insulation can be of the composition type, ¦ i.e., constituted by paper impregnated with the usual compositions, of the oil-filled type, i.e., constituted by paper and low viscosity oil, of the "gas" type, i.e., 8 constituted by paper impregnated with compositions or 19 pressurized with inert gases, and of the extruded type, e.g., constituted by polyethylene or elastomeric composi-tions. Moreover, said process can be applied both to 22 cables for the transmission of electric power and to 23 telephone and telegraph cables.
24 All of these cables are characterized by the presence, in their structure of various tapes and sheaths, 26 screens or armors, which are able to carry out various 27 functions. Many of these parts of the cables are made 28 of metal, and in particular, with respect to the outermost 29 ones, they can be chemically attacked by particular fluids (liquids or gases) which may be present in localized zones 3l of the medium in which the cable is immers~d.

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~ ~ Said corrosive fluids can be generated by gaseous 2 Isources at the sea or lake bottom on which the cable has l llbeen laid, for deep endogenous formation, or be generated

4 1l in the water-sand system, owing to the presence of particu-`I !

5 ¦~lar seaweeds or micro-organisms. Particularly high con-

6 ¦¦ centrations of said fluids can be found in the zones in

7 , immediate proximity to the shore, where, as a rule, the

8 ¦ cable must be laid below the bottom or, when the cable is g ~ completely embedded in the sand of the bottom, because of ~ the structure of the system in which it is situated~
Il ~ Generally speaking, submarine cables are wrapped 12 ¦ with a taping of bitumen-impregnated jute, but such 13 wrapping is quite unable to prevent said corrosive fluids 14 from coming into contact with the metal armor of the cable, which is therefore the most suscep~ible to the corrosive action. Other sheaths which might be present below the ¦ armor, between the latter and the other metal parts of the 18 ¦ cable, even if they are made of materials having good im-19 1 permeability characteristics, are unable to avoid the result that, after a certain time which might be relatively 21 long but which is shorter than that required for the useful 22 life of a cable, said fluid may penetrate the sheaths, 23 attacking said metal parts, and may consequently cause 24 irreparable damage of an electrical or mechanical nature.
2s A particularly frequent corrosive fluid is sulfhydric acid 26 (H2S or hydrogen sulfide), generated by gas evolving 28 sources or developed in the system in which the cable is immersed.
29 The present invention has, as one object, the providing of a process for protecting a submarine electric 31 cable from the corrosive action exerted on the outermost .

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metal parts with which it is prov:icled, by fluids which may be present inlocalized zones of the water medium in which the cable is immersed.
Our invention may be generally defined as a process for providing a submarine electric cable with a protective layer which protects the cable against corrosive fluids in the medium in which the cable may be immersed, said cable having ~t least one inner electric conductor surrounded by insulation which, in turn, is surrounded by a metal, mechanically reinforcing layer, said process comprising performing, during or subsequent to the laying of the cable, the steps of: (a) depositing a layer of a protective composition comprising a non-metallic binder loaded with a chemical compound which will react with sulfhydric acid and render the latter substantially - chemically inert with respect to the metal of said mechanically reinforcing layer into at least one channel shaped element which is adapted to fit partly around said cable with the composition therein and which is made of a material substantially impermeable to fluids; (b) engaging said cable with said composition in said element; and (c) applying to said cable more of said composition and a second channel shaped element which is made of a substantially fluid impervious material and which interfits with the first mentioned element, said composition and said second element being deposited on said cable in a manner which causes said cable to be surrounded by said composition which in turn is surrounded by interfitting said elements to provide a protective tubular envelope around said cable.

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Conveniently, the process consists in the steps of laying successive port:ions of said cable into correspondillg portions of a container obtained by connecting together a pre-establ:ished number of said first elements, having the sllape of a channel and partially filled with said composition of material, of covering each of said cable portions laid in the corresponding portions of the container with a quantity of said composition in order to obtain, around the cable, a layer of composition of substantially uniform thickness, and of positioning on said container, and connecting to it, said second elements having the shape of a channel so as to provide said continuous outer envelope for containing said layer of composition.
Other objects and advantages of the invention will .

_ ~ _ ':, 10758~;ti I Ibe apparent to those skilled in the art from the following 2 Idetailed description of the presently preferred embodiments ~ ,~thereof, which description should be considered in con-4 1~ junction with the accompanying drawings in which:
¦ Fig. 1 is a diagrammatic perspective view of 6 ,¦ a cable portion provided with a protective sheath 7 1 according to the first embodiment of the process ~ of the invention;

9 Fig. 2 is a diagrammatic, perspective view o of the cable portion shown in Fig. 1 having a second armor on the protective sheath;
12 j Figs. 3 and 4 are perspective views of two 13 1 channel-shaped elements which interengage to pro-vide an envelope for the cable and are used in ¦ the second embodiment of the process of the invention;
¦ Figs. 5 and 6 are cross-sections of the 8 elements illustrated in Figs. 3 and 4, respectively;
I Fig. 7 is a longitudinal section of the cable obtained with the channel-shaped elements of Figs. 3-6 and produced according to the second 23 embodiment of the process of the invention;
24 Fig'. 8 is a cross-section of the embodiment shown in Fig. 7; and Figs. 9-12 are perspective views of structures 7 obtained by using the channel-shaped elements during , successive steps of the process according to said 2~ ¦ second embodiment.
As stated hereinbefore, the process of the in- I ;, 31 vention is intended to protect a submarine electric cable against the corrosive action exerted on the outermost metal ~0758 I
I Iparts with which it is provided, by fluids which may be 2 present in localized zones of the medium in which the cable ~ is immersed. ~n electric cable of this type (a portion of 4 I which is diagrammatically represented in Figs. 1 and 2) may l~comprise an electrical conductor or conductors, any desired 6 '¦insulation known per se and several layers of tapes, sheaths 7 and screens, intended to carry out various electrical and 8 1 mechanical functions.
Externally to said parts of the cable which, for o simplicity's sake, have not been individually illustrated ¦ in Figs. l and 2 but have simply been identi~ied as a 12 ~ whole by the reference numeral l, an armor 2 is always 13 1 present in submarine cables which, as is known, is normally 4 constituted by a plurality of metal wires of any section and helically wound up so as to originate a continuous outer metal armor, such armor being intended to withstand the high mechanical tension stresses acting on the cable, 8 1 particularly during the laying of the cable.
9 ll According to the process of the present invention, 1 a continuous protective element 3 is arranged around the 21 Icable portion 1, externally to the armor 2. Said element 3 22 lis substantially impermeable to fluids (gas and liquids3 23 ¦ present in the medium in which the cable is immersed and 24 contains compounds of heavy metals.
According to the first embodiment of the process 26 of the present invention, said protective element 3 can be 27 applied directly, during the manufacture of the cable, by 28 merely applying around the armor layer 2 a continuous 29 sheath made of any plastically deformable, polymeric 1 material, impermeable to fluids, having uniformly dispersed therein compounds of heavy metals. More particularly, the ~o~

I , sheath can be constituted by a compound based on a natural 2 ll or synthetic extrudable polymeric material, preferably, a ~ butyl-rubber base compound, comprising lead oxides unifoxmly 4 111 dispersed in it, lead oxides being the compound of a heavy 5 1¦ metal. The amount by weight of said oxides is, preferably, 6 1 between 5% and 30~ with respect to the total weight of the 7 1 compound forming the sheath, but other proportions may be 8 ~ used. The sheath can be extruded directly on the armor 2 g I of the cable, according to methods known per se. According to this constructional arrangement, the protective element 3 1 in the form of a sheath is, therefore, able to provide a 12 dual barrier against the passage of the fluids ~gas or 13 liquids and their mixtures) which can chemically attack the 4 ¦ metal parts of the cable. Such protective action is pro-vided, first of all, in a physical or mechanical manner, by ¦ virtue of the impermeability characteristics possessed by 7 ~ the sheath, and secondly, in a chemical manner, by virtue of the presence of the compounds of heavy metals incorporated 9 in the sheath which react chemically with various fluids to neutralize the latter.
21 The process of the invention according to this 22 first embodiment can conveniently comprise the further step 23 of applying on the protective element or sheath 3 another 24 armor 4 (Fig. 2) also constituted, for example, by a 2s plurality of helically wound up metal wires. Said second 26 armor can advantageously have a radial thickness (depending 27 on the diameter of the relative wires and on the number of 28 layers formecl by them) much smaller than that of the main 29 armor 2. In fact, the dimensions of the armor 4, as des-cribed hereinafter, should be just sufficient to protect 31 mechanically the underlying sheath 3 against damage which . , - ' . ':

1075~6 ~ ~migh-t be caused during the laying of cable itself.
t 1~ It is evident that the protection of the cable . Ilwhich can be obtained by the process of the invention is a 4 1~ result of the barrier against the corrosive fluids which 5 1l otherwise would attack the metal parts of th cable, and 6 the various sheaths underlying the armor its~lf, after 7 having easily passed throu~h both the usual conventional 8 i protections which are arranged around the armor 2 of the 9 1 cable, such as tapings of layers of bituminized fabrics.
The protective action is provided, in particular, 11 ¦ with respect to the fluids which are able both to attack the 12 1 metal parts of the cable and to penetrate, normally by diffusion, into the normal sheaths of deformable materials 4 present in the cable. Fluids of this type are, in particu-~ lar, the sulfhydric acid (H2S or hydrogen sulfide), generated 6 1 by gaseous sources sometimes present on the watar bottoms, ¦ and generated by the combined action of particular seaweeds 18 i and/or micro-organisms present in the medium (sand and I ¦ water) in which the cable is immersed.
1 As stated hereinbefore, the protective action is 21 l effected both in a physical/mechanical way and in a chemical t2 ¦ way. By virtue of the first way, the penetration by 23 diffusion of said fluids in the sheath 3 is reduced, if not avoided, owing to the characteristics of impermeability of the sheath itself. By virtue of the second way, the fluids 26 which partially penetrate inside the sheath in the indicated manner are neutralized and made chemically inactive, as a 28 consequence of the reaction of the compounds of heavy metals 29 (for example, oxides) with said fluids. The reaction pro-ducts (for example, sulfides) do not attack chemically the 31 metal parts of the cable. It is to be taken into account ~07~86;~i I that, a~ has been found from tests carried out on protections t 1l provided according to the process of the invention, the ob- ~
~ l~jects of the invention are achieved in the best way if the im- .
4 l~permeability characteristic of the sheath 3 and the presence , of the comp~unds of heavy metals are combined.
6 ~ If there were only good impermeability of the 7 1 sheath, as would be obtained if the latter were constituted 8 1 by a compound based on a fluid-impervious natural or synthetic .
polymeric material, a certain amount of penetration of the 0 sheath would take place after a service time whlch might be relatively long, but which would be much shorter than that 2 normally required for the life of a cable. Only by in-cluding said metal compounds in said fluid-impervious poly-meric material is it possible to provide a protective element for the cable which is able to stop the penetration of said 7 fluids, neutralizing them as they pxogressively migrate in the sheath 9 Figs. 3-12 refer to the second embodiment of the process according to the invention.
Before describing the various steps of the second 21 embodiment, it is advisable to examine the channel~shaped 23 elements used during said process to obtain a substantially 24 continuous envelope, such elements being shown in Figs. 3-6.
The elements 11 and 12 have a curved wall, lla 26 and 12a, shaped in such a way as to provide a part of an envelope in the form of a channel. In the illustrated em-27 bodiment, the walls lla and 12a are substantially cylindrical as can be best seen in Figs. 5 and 6, and a section of each of said elements 11 and 12, taken with a plane perpendicular 31 to the longitudinal axis of the element itself, conforms to part of a cixcular ring with center angles a and ~, greater .
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~758~6 I ¦than 180. The elements 11 and 12 are of two different 2 'I types, slnce the element 11 has a center angle smaller than ~ that of the element 12 (~ > ~). An enlaryed terminal end 4 11 13a and 13b of each element has its inner and outer diameter 1 greater than the corresponding diameters of the remaining 6 ¦ parts of the element, so as to allow the other terminal end 7 1 of another element to be inserted within the enlarged ends 8 ¦ 13a and 13b of the preceding element, as will be noted Erom g ¦ the section of Fig. 7 which shows elements 11 and 12 of the two types and shows ends 13a and 13_ encasing the opposite ends of contiguous elements 11 and 12.
For convenience, a support 14 is mounted on and 3 secured to the interior, bottom surface of each element 11.
The support 14, made, for example, of wood, has a substanti-ally cylindrical surface 15 (Figs. 3, 8 and 9) intended to bear against said bottom surface. The support 14 can be secured to the relative element in any suitable manner, 8 for example, by means of a screw 16 ~Fig. 8).
19 ~he elements 11 and 12 are made of an elastically deformable, synthetic polymeric material having good 21 characteristics of impermeability to fluids, for example, 22 polyvinyl chloride or polyethylene.
23 This second embodiment of the process can be 24 carried out to build up, in the way which will be described, the protection of a submarine electric cable which has already 26 been laid and, preferably, of a cable which is being laid.

27 In the first case, the process can be effected after the 28 true cable laying operation, while in the second case, it is effected simultaneously with the laying operation.
: 31 The process carried out simultaneously with the ~ laying of a new cable will be initially examined. The first

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I ~ step of the process produces a structure obtained by con- I
2 ~necting a pre-established numher of elements 11 of the first ¦
~ Itype, so as to build up substantially a first portion of 4 1 container, in the form of a channel, indicated with 17 in 5 1I Fig. 9-¦ To obtain said portion, the various elements 11 7 11 are coupled together by inserting into the enlarged end 13a 8 1 of each of them the other end o~ the contiguous element 11.
9 ¦ Said elements 11 are secured together in any appropriate o ¦ manner, for example, by means of screws 18, inserted between ¦ the walls of the coupled edges, such as by using, for con-venience, a tool 19 as shown in Fig. 9. The tool 19 com-13 ~ prises substantially a U-shaped bridge 20, which can be in-serted astride each pair of edges, a bushing 21 for guiding the screws 18 and a manipulating wrench 22 which can be 6 operated by hand and which is provided with a threaded part ¦¦ to be inserted in a threaded hole of the bushing 21. By 18 ¦I rotating the wrench 22, it is possible to cause axial trans-¦¦ lation of the screw 18 previously inserted in the bushing 21 ¦ itself. ~ -

11 A layer of composition 25, of such a thickness as 22 to slightly cover the supports 1~, is applied in each ele-23 ment 11 of the so-obtained container 17. Said composition 24 25 comprises substantially one or more compounds of heavy 2~ metals, dispersed in a suitable binding agent, impermeable 26 to fluids. In this case, said binding agent, besides 28 exerting a mechanical function able to keep the metal oxides 29 inside the composition, permits the forming of a structure having good fluid impermeahility characteristics. ~o this end, bitumens of various kinds may be used. In particular, 31 bitumens having different viscosities, which are able to pro-1~75~66 Ivide~ by means of an appropriate proportioning, a composition 2 1 of the desired, pre-established consistency for a certain I~period of time, may be prepared according to the methods 4 1l described hereinafter. Conveniently, the composition may s I be prepared by using as the compound of a heavy metal, iron 6 oxide easily available as purple ore. The binding agent 7 ~ may comprise a bitumen "55" and a bitumen "8E". A preferred 8 1 composition of this type comprises from 70 to 90 parts by 9 weight of purple ore, from 5 to 15 parts by weight of o I bitumen "55" and from 5 to 15 parts hy weight of bitumen "8E". The first of said bitumens has a medium viscosity while the second is very fluid. Therefore, if they are 3 mixed in the amounts indicated, a composition is obtained which is malleable for a time period sufficient for the S ¦ laying of the cable.
16 1 The composition can be conveniently obtained by l? adding by stirring the bitumen "8E" to the bitumen "55"
8 heated at a temperature of 110C - 120C, and by subse-19 ~uently adding purple ore, always by stirring.
According to an alternative method, the composi-21 ¦ tion can be prepared by adding a mixture of bitumen "55"
22 and of bitumen "8E", heated at a temperature of about 23 140C, to purple ore heated at 60 - 70C while stirring.
24 In a step of the process, subsequent to that 2s described and illustrated in Fig. 9, a portion of cable 26, 26 for example, the parts 1 and 2 of Figs. 1 and 2, is laid on 27 the layer of composition 25 (Fig. 10) To carry out this 28 step, the conventional methods used for laying submarine 29 cables may be followed. For example, if the cable 26 is 31 underwater, the cable 26, appropriately supported by tie rods or wire rope 27, in turn connected to floats which are 10758~;6 1 llgradually deflated, is allowed to slowly descend on the 2 11 layer 25.
¦ Subsequently, a layer 28 in an appropriate amount is applied (Fig. 11), for example, by hand, on a part of the ~ cable 26. In a successive step, the layer of composition 6 1 applied on the cable can be rendered compact and smooth by 7 ¦ using, for example, a tool 29 having a curved wall able to 8 shape correspondingly the surface of the layer 28 itself.
9 In a next step, the elements 12 (Fig. 12) are o arranged on the so-prepared structure. The assembling of 1l each of said elements 12 is effected by deforming the rele-

12 vant end 13b radially and elastically and by pushing it

13 radially to overlap and couple it to a corresponding ele-4 ment ll. Then, by exerting on said element 12 forces sub-stantially directed towards the axis of the structure, the remaining part of the element 12 is at first radially de-7 formed and then assumes a position completely superimposed 8 on the corresponding element ll, as is clearly visible in 19 the section of Fig. 8.
¦ It is preferable to assemble each element 12 in 1 an offset position with respect to the elements 11 of the 22 container underlying it. By constructing it this way, a more nearly continuous envelope is obtained, a portion of 24 such envelope being represented in Fig. 12. Such envelope encloses the layers 25 and 28 of composition having a sub-26 stantially uniform thickness and such layers enclose the 27 cable 26. The composition forming the layers 25 and 28 28 will flow during or after the application of the elements 12 29 and fill any crevices between the elements 11 and 12 and 3l between the ends of successive elements, thereby providing a seal therebetween.

~-J~7~ 6 1 By proceeding in the described manner, the pro-2 ~ tection of the whole cable can be carried out in successive 3 I portions.
4 I The supports 14 sust:ain the cable 26 in a position 5 '1I substantially coaxial to the envelope, even if sinking of 6 1I the composition underlying the cable 26 should take place.
7 ~ If it is desired to protect the cable 26 after it 8 ~Ihas been laid, the steps of the process as described are 1 9 l~preceded only by the steps of removing the cable from the o llsand and, if necessary, in order to be able to arrange the corresponding portions of the container 17 (Fig. 9) in which said cable portion will be laid, the step of raising the cable 26 from the bottom.
It is evident that the so-obtained protection com-I prises an outer envelope constituted by the channel-shaped ilelements 11 and 12 which confer a good impermeability to 1 17 ¦the structure. Said impermeability is improved by the layers 25 and 28 of composition applied inside said ele-9 ¦¦ments 11 and 12, by virtue of the presence of the binding l agent (bitumen). In this way, in consequence of said 21 ~ impermeability, there is a first action (physical/mechanical) 22 to prevent corrosive 1uids from coming into contact with 24 ;the metal armor of the cable.
I Moreover, the compounds of heavy metals present ¦in the composition (purple ore) provide a second barrier 26 (which acts substantially by chemical reaction) against the 27 penetration o~ said fluids. Therefore, substantially, 28 the action of the protection obtained according to this 29 second embodiment of the process is ~uite similar to that of the first embodiment.
31 It will be apparent to those skilled in the art 107Sl~it;6 I that the compound included in the protective sheath will be 2 l selected in accordance wi-th the nature of the compound or 3 I compounds in the fluid which is to be neutralized and that 4 ~ metal compounds other than those named herein may be used.
1 Furthermore, it will also be apparent that more than one 6 ¦ compound may be included in the protective sheath.
7 ! Although presently preferred embodiments have 8 I been illustrated and described, it will be apparent to those 9 'I skilled in the art that modifications may be made without o 1~ departiny from the principles of the invention.

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Claims (16)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for providing a submarine electric cable with a protective layer which protects the cable against corrosive fluids in the medium in which the cable may be imm-ersed, said cable having at least one inner electric conductor surrounded by insulation which, in turn, is surrounded by a metal, mechanically reinforcing layer, said process comprising performing, during or subsequent to the laying of the cable, the steps of:
depositing a layer of a protective composition comprising a non-metallic binder loaded with a chem-ical compound which will react with sulfhydric acid and render the latter substantially chemically inert with respect to the metal of said mechanically rein-forcing layer into at least one channel shaped ele-ment which is adapted to fit partly around said cable with the composition therein and which is made of a material substantially impermeable to fluids;
engaging said cable with said composition in said element; and applying to said cable a further amount of said composition and a second channel shaped element which is made of a substantially fluid impervious material and which interfits with the first mentioned element, said composition and said second element being deposited on said cable in a manner which causes said cable to be surrounded by said composition which in turn is surrounded by interfitting said elements to provide a protective tubular envelope around said cable.

2. A process as set forth in claim 1, wherein said elements are formed from a synthetic polymeric material which is substantially fluid impermeable.

3. A process as set forth in claim 2, wherein each of said elements is formed with an enlarged end for receiving the opposite end of another element and wherein said elements are longitudinally interconnected with other elements by plac-ing said large end of one element over the opposite end of an-other element.

4. A process as set forth in claim 3, wherein the interconnected ends are secured together by fastening means.

5. A process as set forth in claim 1, wherein said layer of composition and said elements are applied to said cable by interconnecting a plurality of said first mentioned elements so as to form a channel, partially filling said channel with said composition, laying a portion of said cable in the composition in said channel so as to cover part of the circumference of said portion with said composition, covering the remainder of the circumference of said cable with further amounts of said composition, applying a plurality of said sec-ond elements over said further composition and engaging them with the elements forming said channel to form a substantially peripherally continuous, substantially fluid impermeable envel-ope around said protective composition.

6. A process as set forth in claim 5, wherein each element is elastic and in cross section, is curved with the cen-ter angle thereof greater than 180° but less than 360° and wherein said second elements are engaged with said elements forming said channel by elastically expanding said second elements over said elements forming said channel.

7. A process as set forth in claim 5, wherein said second elements are placed with their ends in offset relation, longitudinally of said cable, to the ends of said elements forming said channel.

8. A process as set forth in claim 5, further com-prising forming said elements from a polyvinyl chloride com-position.

9. A process as set forth in claim 5, further com-prising placing supports for said cable within said channel and spaced in the direction longitudinally of said channel prior to laying said cable in said composition in said channel.

10. A process as set forth in claim 1 or 5, wherein said composition is prepared by mixing purple iron oxide ore with at least one bitumen.

11. A process as set forth in claim 10, wherein said composition is prepared by mixing 70 to 90 parts by weight of said purple ore, 5 to 15 parts by weight of bitumen "55 and 5 to 15 parts by weight of bitumen "8E".

12. A process as set forth in claim 11, wherein said bitumen "55" and bitumen "8E" are stirred together and heated at a temperature of 110° to 120°C and then said purple ore is added while stirring.

13. A process as set forth in claim 14, wherein said bitumen "55" and said bitumen "8E" are mixed and heated to about 140°C and are then added to said purple ore, heated to 60° to 70°C, while stirring.

14. A process as set forth in claim l wherein said chemical compound is a metal compound.

15. A submarine electric cable comprising at least one inner electric conductor surrounded by insulation which, in turn, is surrounded by a mechanically reinforcing metal layer, a layer of a protective composition surrounding said metal layer, said composition comprising a non-metallic binder loaded with a chemical compound which will react with sulfhydric acid and render the latter substantially chemically inert with res-pect to the metal of said reinforcing layer, and a plurality of channel-shaped elements of a substantially fluid impervious material surrounding said layer of protective composition, said elements being interengaged and forming a longitudinally ex-tending, protective tubular envelope around said layer of com-position.

16. A cable as set forth in claim 15, wherein said chemical compound is a metal compound.