When metal is exposed to water or moisture, marine-grade metal may be needed to prevent the material from failing under the conditions. To be considered marine grade, the material must be able to resist the corrosive effects commonly found in water environments. To achieve this, special alloying elements are added to these grades to prevent corrosion.
Carbon and alloy steel
Aluminum
Stainless steel
Copper
Bronze
Brass
Galvanized steel
Most carbon steel is not suitable for marine environments, however, there are several marine-grade carbon steels available. AH36, DH36, and EH36 are all examples of commonly used marine-grade carbon steel approved by the Bureau of Shipping. Compared to ASTM grades, these grades will have slightly more alloying elements such as manganese and chromium, which helps achieve greater strength and greater corrosion resistance. Alloy steel also comes in marine grades. Grades such as MD, ME, MF, MG provide the strength that common alloy steels are known for and are approved by the Bureau of Shipping for shipbuilding applications.
Applications: Structural shipbuilding and other offshore structural applications
There are several different grades of aluminum suitable for marine conditions. Marine grade aluminum, in most cases, is limited to grades 5XXX and 6XXX. Grade 5052 is an excellent marine grade when formability is required. If strength is more of a concern, level 5083 is a good choice. 6061-T6 is an all-around popular aluminum grade also commonly used in marine applications. It has very good corrosion resistance and is precipitation hardened. In most cases, these grades have additional chromium and manganese to help protect them from corrosive marine conditions.
Applications: Structural shipbuilding, hulls, boat lifts, docks and other offshore structural applications
All grades of stainless steel have some degree of corrosion resistance, however, several grades are more suitable than others for use in marine environments. Grade 316 is probably the most commonly used grade of stainless steel in marine applications. It contains more molybdenum than other austenitic stainless steels, which helps resist pitting and other corrosive effects of salt water. Grade 304 is another marine grade stainless steel, although it has less molybdenum than grade 316, making it a less ideal choice in chlorine-rich environments.
Applications: Marine accessories, marine fasteners and marine structures
There are several copper-nickel alloys suitable for marine applications. Examples include C70600, which contains nickel and manganese to help resist corrosion. C71500 is also able to withstand marine conditions and is similar in composition to the C70600 alloy, except that it contains more nickel in its chemical composition.
Applications: Water pipes, desalination equipment, marine accessories, fasteners, valves and pumps
Silicon bronze alloys such as C65500 and aluminum bronze alloys such as C95400 are more resistant to marine environments than other bronze alloys. Alternatively, Phosphor Bronze Alloy C51000 is another common grade suitable for marine applications.
Applications: Propellers, propeller shafts, pipes and marine fasteners
Navy brass, or naval brass as it is commonly called, comes in a variety of alloys. Alloys C46200 and C46400 have zinc and tin added to make the brass alloy corrosion-resistant in wet and even underwater applications. Alloys C48200 and C48500 are similar except that they contain more lead in their chemical compositions.
Applications: Pipes, Marine Fittings, Marine Fasteners and Pumps
Galvanized steel is suitable for certain marine environments. Zinc coatings generally perform better at the low temperatures of fresh water than in salt water. Salt water contains chloride, which causes zinc to corrode quickly. High temperatures will cause corrosion to occur faster.
Application: Marine structures
Shanghai Yixing Technology is specialized in sheet metal manufacturing for marine industry for more than 20 years. The most important factor we need to consider for marine industry parts is the corrosion resistance because the seawater and marine environments are much more corrosive than normal environments. How to ensure the durability of the product and corrosion resistance is very important. As a professional sheet metal fabrication factory, we are very serious in material selection. Not only do we use the marine grade material, but also we will choose the top 3 mill factory in China like Baosteel, Wuhan Iron and steel etc. Equipped with most advanced machines, we can make qualified sheet metal parts for marine industry.
Take the gangway production as an example:
The gangway is a device that connects the ship hull to the dock and allows people to get on and off the ship. The gangway process technology mainly includes two aspects: gangway manufacturing and gangway installation. Gangway manufacturing is an important part of gangway process technology.
In gangway manufacturing, the first step is to select the appropriate material. Commonly used materials for gangways include aluminum alloy, steel and fiberglass. Aluminum alloy gangways are lightweight, corrosion-resistant, and suitable for all parts of ships; steel gangways have a stable structure and strong load-bearing capacity, and are suitable for heavy-load ships; fiberglass gangways have the advantages of light weight, corrosion resistance, and fatigue resistance, and are suitable for general ships.
Secondly, design and drawing are required in the manufacturing of gangway. Based on actual needs and usage requirements, designers will design the function, shape, size, etc. of the gangway and produce detailed drawings. Information such as the size, material, and processing requirements of each component will be marked on the drawing to facilitate processing and manufacturing by workers.
Then, the processing and manufacturing of the gangway are carried out. The manufacturing process of the gangway includes blanking, bending, welding, cutting, drilling and other processes. During the processing process, precise operations are required according to the drawing requirements to ensure that the quality and size of the gangway are accurate. At the same time, surface treatment is also required, such as spraying anti-corrosion paint, painting, etc., to improve the corrosion resistance and aesthetics of the gangway.
Gangway installation is another important link in gangway technology. During the installation of the gangway, the position needs to be measured and marked first. According to the design requirements and actual conditions, the construction personnel will measure and mark the dock and ship to determine the location of the gangway installation.
Then, fix and install the gangway. There are many ways to fix the gangway, the most commonly used ones are welding fixation and bolt fixation. For large ships and heavy-duty ships, welding is usually used to ensure the stability of the gangway; for light ships, bolts are usually used to facilitate replacement or disassembly.
Finally, the ramp is tested and accepted. After the installation of the gangway is completed, testing and acceptance are required to ensure the safety and reliability of the gangway. The test content includes the load-bearing capacity test of the gangway, wind resistance test, etc. The acceptance includes inspection and measurement of all parts of the gangway to ensure that the gangway meets the design requirements and relevant standards.
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