Section 1 General
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Construction & Classification of Submersibles & Diving Systems, July 2022 - Part 4 Exostructure, Stability and Corrosion Protection - Chapter 3 Corrosion Protection - Section 1 General

Section 1 General

Parent topic: Chapter 3 Corrosion Protection

1.1 Scope

1.1.1 This Chapter gives methods of corrosion protection that may be considered for various locations but the selection should take into account such factors as the following:
  1. Application, environmental aspects;
  2. Design life;
  3. Weight aspects;
  4. Type of material;
  5. Ease and frequency of inspection;
  6. Toxicity;
  7. Electrical hazards and maintainability of protection on surfaces.

1.2 Application

1.2.1 All steelwork is to be suitably protected against loss of integrity due to the effects of corrosion. Suitable protective systems may include coatings, metallic claddings, cathodic protection, corrosion allowances, or other approved method. Combinations of methods may be used.

1.2.2 The type of protection is to be suitable for the intended location and for this purpose the steel structure should be considered in the terms as indicated in Pt 4, Ch 3, 1.2 Application 1.2.3 to Pt 4, Ch 3, 1.2 Application 1.2.5.

1.2.3 Intermittently submerged steelwork may be protected by:
  1. Extra steel in excess of that needed for strength.
  2. Coatings.
  3. Sacrificial anodes where the immersion period is of adequate duration.
1.2.4 Closed flooded compartments may be protected by:
  1. Extra steel in excess of that needed for strength.
  2. Coatings.
  3. Cathodic protection.
  4. Corrosion inhibitors together with biocides.
  5. Chemicals for pH control together with biocides.
  6. Sacrificial anode.
1.2.5 Free flooding compartments are to be avoided as far as possible. Any which cannot be avoided should be protected by:
  1. Extra steel in excess of that needed for strength.
  2. Coatings.
  3. Cathodic protection.
  4. Sacrificial anode.

1.3 Plans and information

1.3.1 In order that an assessment may be made of protection systems, full details as outlined in Pt 4, Ch 3, 1.3 Plans and information 1.3.2 to Pt 4, Ch 3, 1.3 Plans and information 1.3.6 are to be submitted.

1.3.2 The following plans and information are to be submitted for all cathodic protection systems:
  1. A surface area breakdown for all areas to be protected.
  2. The resistivity of the sea water.
  3. All current densities used for design purposes.
  4. The type and location of any reference electrodes, their methods of attachment and the method for transmitting the potential data.
  5. Full details of any coatings used and the areas to which they are applied.
  6. Details of any electrical bonding or insulation.
1.3.3 In addition to the information required by Pt 4, Ch 3, 1.3 Plans and information 1.3.2 the following plans and information are to be submitted for all sacrificial anode systems:
  1. The design life of the system (years).
  2. Anode material and capacity of anode material (A h/kg).
  3. The dimensions of anodes, including details of the insert and its location (cm).
  4. The net and gross weight of the anodes (kg).
  5. The means of attachment.
  6. Plans showing the location of the anodes.
  7. Calculation of anodic resistance as installed and when consumed to their design utilization factor.
  8. Closed circuit potential of the anode material (V).
  9. Details of any computer modelling.
  10. The anode design utilization factor.
1.3.4 In addition to the information required by Pt 4, Ch 3, 1.3 Plans and information 1.3.2, the following plans and information are to be submitted for all impressed current systems:
  1. The anode composition, and where applicable, the thickness of the surface plating, consumption and life data.
  2. Anode resistance, limiting potential and current output.
  3. Details of construction and attachment of anodes and reference electrodes.
  4. Size, shape and composition of any dielectric shields.
  5. Diagram of the wiring systems used for the impressed current and monitoring systems including details of cable sizes, underwater joints, type of insulation and normal working current in the circuits, and the capacity, type and make of protective devices.
  6. Details of glands and size of steel conduits.
  7. Plans showing the location of anodes and reference electrodes.
  8. If the system is to be used in association with a coating system then a statement is to be supplied by the coating manufacturer that the coating is compatible with the impressed current cathodic protection system.
1.3.5 The following plans and information are to be submitted for all coating systems:
  1. Evidence that any primers used will have no deleterious effect on subsequent welding or on subsequent coatings. See also Pt 4, Ch 3, 3.2 Prefabrication primers.
  2. Details of the painting specification with regard to:
  3. The generic type of the coating and its suitability for the intended environment,
  4. The methods to be used to prepare the surface before the coating and the standard to be achieved. Reference should be made to an established International or National Standard.
  5. The method of application of the coating.
  6. The number of coats to be applied and the total dry film thickness.
  7. Details of the area to be coated.
1.3.6 In addition to the information required by Pt 4, Ch 3, 1.3 Plans and information 1.3.4, for all coating systems the following may also be required:
  1. When a coating contains aluminium and is intended to be used in areas where flammable gases may accumulate, a statement from an independent laboratory confirming that appropriate tests have shown that the coating does not increase the incentive sparking hazard in the area to which it is applied, or
  2. where a coating is to be applied in accommodation spaces, machinery spaces and areas of similar fire risk, a statement that the coating is not formulated on a nitrocellulose or other highly flammable base and has low flame spread characteristics in compliance with IMO FTP Code - International Code for Application of Fire Test Procedures – Resolution MSC.61(67) or any other equivalent national specification is required.
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