Section 3 Material Protection

301. General

1. All craft, complying with these rules, are to apply material protection.

2. All surfaces which are not resistant to the marine environment are to be protected against corrosion.

3. Material protection, not identified in this chapter, is to comply with Ch 3, Sec 2.

302. Approval

Specifications of corrosion protection systems, (i.e., for coating, cathodic protection, etc.), are sub- ject to approval.

303. Corrosion protection

1. Antifouling paint is to be applied over anticorrosion coating.

2. Coatings are not to contain copper or other constituents which may cause galvanic corrosion.

3. Specifications for coating including antifouling, are to state :

(1) Metal surface cleaning and treatment before application of primer coat, including welds and edges

(2) Build-up of coating system with individual coats

(3) Curing times and overcoating intervals

(4) Acceptable temperatures of air and metal surface, and dryness/humidity conditions during above operations

(5) Thickness of individual and final coating

304. Other metallic materials in contact with aluminium

If other metallic materials in propeller, etc. are to be used on an aluminium hull, provisions are to be made to avoid galvanic corrosion. Acceptable provisions are either one or a combination of the followings :

(1) Coating of water/moisture exposed surfaces

(2) Electrical insulation of metals which differ from each other

(3) Cathodic protection

305. Cathodic protection

1. Cathodic protection of aluminium hull can be obtained with aluminium or zinc sacrificial anodes or impressed current.

2. Specifications of cathodic protection system include :

(1) Area to be protected

(2) Current density demand

(3) Anode material and manufacturer

(4) Calculation of service life and estimated protective potential to be obtained.

3. If impressed current systems are applied, precautions to avoid overprotection by means of anode screen and overprotection alarm are to be taken.

306. Connections between steel and aluminium

1. If there is risk of galvanic corrosion, a non-hygroscopic insulation material is to be applied be- tween steel and aluminium.

2. Aluminium plating connected to a steel boundary bar is as far as possible to be arranged on the side exposed to moisture.

3. Direct contact between exposed wooden materials, and aluminium is to be avoided.

4. Bolts with nuts and washers are either to be of stainless steel or cadmium plated or hot galvanized steel. The bolts are in general to be fitted with sleeves of insulating materials.