Overview

Ships are the important maritime tools for people, and they need to move at sea, so maintaining the life of the ships in the flowing sea water is crucial. This article will discuss the application of Monel alloy in ship industries.

Corrosion-resistant Materials for Ships

Corrosion is one of the most important factors affecting the normal use of ships, and it directly affects the availability and voyage rate of ships. In the past, seawater corrosion-resistant materials used on ships were mainly copper alloys synthesized by adding other metal elements to copper elements. In many systems such as fire fighting systems, water curtain systems, daily seawater systems and cooling water systems, the material of alloy pipes and alloy pipe fittings is copper alloy. In long-term use, copper alloys have exposed the problems of being intolerant to sulfide corrosion and high corrosion rate in flowing seawater. Once a ship with copper pipes for fire fighting was delivered to the ship less than a year ago, the pipeline leaked due to pitting corrosion. Researchers investigated a warship that had been in service for nearly ten years and found that the ship’s seawater system leaked serious and more than 50% of the valves have leaks. A considerable part of them are internal leakage caused by valve disc corrosion or valve stem wear. Although later new materials such as B10 pipes are used in the seawater system of new ships, the problems of corrosion and leakage are still very serious. For this reason, people continue to explore the application of new materials and new processes on ships.

Performance Analysis of Monel Alloy

Monel alloy is a nickel alloy with metallic nickel as the main component and metallic copper as the secondary (contains about 30% copper). It has good physical, mechanical and chemical properties. Its corrosion resistance is better than copper, nickel and copper alloys. Among them, Monel 400 and Monel K-500 alloys are mainly used on ships. At present, these two alloys are produced in China. If you need it, you can contact AEETHER.

Monel alloy is characterized by good corrosion resistance in a wide temperature range, strong corrosion resistance under various air and water conditions, and the corrosion rate is not more than 0.03mm/year. In the case of severe temperature changes, water impact and carbon dioxide erosion, the corrosion rate is not more than 0.025mm/year. The following table shows the corrosion rates of several different metals and alloys at different seawater flow rates. It can be seen from the table that Monel alloy has a lower corrosion rate than copper alloys and other metals, and its corrosion rate is hardly affected by the seawater flow rate. This is a characteristic that general copper alloys, including copper-nickel alloys, do not possess.

Application of Monel Alloy in Ship Industries

The main components of Monel 400 alloy are about 2/3 nickel and 1/3 copper. It has excellent comprehensive properties and can be widely used to manufacture many products with good corrosion resistance and high mechanical strength. The alloy has good corrosion resistance to seawater, dilute sulfuric acid, strong alkali, phosphoric acid, fatty acid, etc., and maintains its strength and rigidity up to 450°C or above, so it is widely used in shipbuilding, chemical, petroleum, pharmaceutical and electronic equipment such as: pump shafts, valve stems, marine propellers, seawater system fasteners, screw joints, key parts of various shafts, gasoline tanks, fresh water tanks, pickling equipment, heat exchangers, nuclear engineering components, etc.

The application range of Monel K-500 alloy is similar to Monel 400 alloy, but due to the addition of metal titanium and aluminum, its overall performance is better than Monel 400. It is used to manufacture high-strength, high-corrosion, non-magnetic parts and products. It is widely used in aviation, navigation and petroleum engineering. The most effective application is the important components of marine piping systems-pump and valve parts such as pump shafts, valve stems, valve discs and etc., which can resist both the corrosion of static sea water and the corrosion of high-speed flowing seawater. It can also be used for parts with impact corrosion resistance, as well as ship propellers, screws, impellers, various fasteners, and marine heat exchangers.

In the world, Monel alloy has a long history of application in various industries, and it is also widely used on ships. According to reports, the fasteners, bolts and nuts used in the British North Sea submarine oil pipeline and the Thames Bridge are all used in conjunction with Monel 400 and Monel K-500; the propellers, key shafts and pump parts of British first-class ships are all made of Monel alloy; Many equipment and systems of the French "Charles de Gaulle" aircraft carrier use Monel material. Because Monel alloy is more expensive, it is difficult to use on a large scale on ships, but the use of Monel material on some key parts can achieve a multiplier effect. For example, during the construction of a new type of ship of the Chinese Navy, the valve disc and stem of the seawater valve were made of Monel alloy. After the ship was put into service, the seawater system valve did not corrode and leak.

AEETHER CO., LIMITED produce nickel alloys for Marine applications. If you have any requirements, you can send inquiry to our E-mail: