Did you know that July is the hottest month of the year? As summer is reaching its peak, everyone is finding different ways to escape the heat. And what better way to do so than to get in the water? From swimming to fishing, water activities are a staple for the summer. However, water isn’t the best for metals. Because of the corrosive agents present in water, metals exposed to water for long periods of time can suffer from corrosion.
At these times, corrosion-resistant metals are the perfect solution!
Corrosion-resistant metals, or marine grade metals, are specially treated to withstand use in bodies of water. Usually, this means adding special alloying elements to the metal to make it resistant to corrosion. Most types of metal offer a corrosion-resistant or marine grade alloy, such as brass, aluminum, steel, and many more.
There are several classes of steel that are suitable for marine applications, such as stainless steel, carbon steel, alloy steel, and galvanized steel. Marine grade stainless alloys usually contain molybdenum, which serves to resist the corrosive effects of seawater. Stainless steel is the ideal material for marine applications and is known as one of the most corrosion-resistant metals. A few questions we are commonly asked are “What number is marine grade stainless steel?” or “What is the best metal for saltwater?”
The answer to both of those questions is 316 Stainless Steel, also known as marine grade stainless steel, because of its superior resistance to rust and excellent pitting corrosion compared to other grades of steel.
Stainless steel is also used for water bottles and coffee mugs, as they are great insulators and resist water corrosion. Other examples of marine applications of steel include marine fittings, boat propeller shafts, deck components for boats and ships, and storage vessels.
Marine grade aluminum is a collection of aluminum alloys in the 5XXX and 6XXX series. The best examples are 5052, 5083, 5086, 6061, and 6083. Aluminum is a popular choice for marine applications due to its low weight, especially compared to steel.
Applications of aluminum include not only hulls, deckhouses, and hatch covers of commercial ships, but also equipment items like ladders, railings, windows, and doors. One example of marine grade aluminum is in the Littoral Combat Ship USS Independence, which sports an all-aluminum hull.
Copper and its alloys
Since antiquity, copper alloys have been used to resist the ravages of the sea. Copper is very versatile with good corrosion resistance in marine atmospheres and seawater.
Copper is also ductile and commonly used for tubing in marine environments. Also, the thermal conductivity of copper make it a popular material for components where rapid heat transfer is essential. However, when seawater conditions are polluted with ammonia and sulphides, higher corrosion rates or pitting can be experienced.
Copper’s properties, both in terms of corrosion resistance and mechanical strength, can be further improved by alloying. There are many copper alloys suitable for marine service. The main groups are copper-nickels, certain bronzes, certain brasses, and beryllium-copper.
For seawater systems, copper-nickel and aluminium-bronze are often preferred. Although other copper alloys are used in marine service and have their specific advantages. Copper alloys differ from other metals in that they have an inherent high resistance to biofouling, particularly macrofouling. This can eliminate the need for antifouling coatings or water treatment.
The marine grades for brass are 464 “naval brass” and 485 “leaded naval brass.” These materials have a small amount of tin added to help deal with corrosion. The 485 includes a bit of lead, making it easier to machine. They are typically used in marine construction, propeller shafts, marine hardware, decorative fittings, shafting, propeller shafts and turn buckles.
In addition to the naval brasses, another notable brass type that does well in water is 280 “Muntz brass. The alloy is named after its inventor, George F. Muntz. He developed the alloy in 1832 as a cheaper alternative for lining ship hulls. You can learn more about Muntz brass here.
Aluminum-bronzes are tarnish-resistant, show low oxidation rates at high temperatures, and are resistant to corrosion in sea water. It also prevents colonization by marine organisms like algae, barnacles, and mussels.
Silicon-bronze offers to its high strength, corrosive resistant material, and non-magnetic properties. This makes it excellent for use in general marine applications, as well as nuts, bolts, pumps, and boilers.