HOW TO CHOOSE SACRIFICIAL ANODES FOR SHIPS

HOW TO CHOOSE SACRIFICIAL ANODES FOR SHIPS

(Comparison of aluminum anodes, zinc anodes, and magnesium anodes.)

With the development of ship anti-corrosion technology, ship owners will have more sacrificial anodes to choose from than ever before. But what are the differences between different anodes and how are they selected? Each anode is suitable for its own environment, so you must choose the most suitable anode. Today, let us explain the performance of aluminum anodes and magnesium anodes.

WHAT IS ELECTROCHEMICAL CORROSION?

If there is no galvanic corrosion, the ship does not have to worry about corrosion problems, but the reality is not like this. Galvanic corrosion occurs when two metals with different activity levels are placed in close proximity to each other in an electrolyte (water). This difference in composition allows electrons to flow from the anode (a highly reactive metal) to the cathode through the electrolyte. You can't see the actual electron transfer with the naked eye, but you will certainly notice the long-term effects of galvanic corrosion over time. Eventually, galvanic corrosion will reduce the weight of the anode and weaken it until dissolution is complete.

As for ships, galvanic corrosion occurs when 

you place metal equipment in the water next to the metal ship. The metals that make up a ship are usually the most reactive metals in water. In this process, water serves as the electrolyte, and the two metals must be adjacent, which is a necessary condition for forming galvanic corrosion. For example, if the ship is made of metal and slightly different metal anchors are used, galvanic corrosion will occur. Obviously, allowing electrochemical corrosion to dissolve the hull is a major disaster, so sacrificing the anode is a necessary part of ship anti-corrosion.

TYPES OF SACRIFICIAL ANODES

As mentioned prior, zinc was the first commonly used metal material for sacrificial anodes. Although zinc works well in some cases, it requires the use of different metals in sacrificial anodes in others. Which metals can be used as sacrificial anodes? In addition to zinc, magnesium and aluminum can also serve as sacrificial anodes. All of these metals are more reactive than the elements used in shipbuilding, so when galvanic corrosion occurs, they corrode faster. Due to the sacrificial anode withstanding the impact of corrosion damage, your ship can be protected from corrosion.

ALUMINUM ANODE OR MAGNESIUM ANODE: WHICH IS MORE SUITABLE?

So, when should aluminum and magnesium anodes be used on ships? Traditional zinc anodes are very suitable for use in salt water, but they are not very useful in fresh water. In addition to this limitation, zinc anodes are also heavy and environmentally unfriendly. In this case, zinc itself is not the only environmental issue. Zinc anodes contain cadmium activators, which are highly toxic to marine organisms.

Due to the widespread supply of zinc, it has been the only option for many years, but there are now better options available in the market. On the contrary, let's consider the capabilities of magnesium and aluminum anodes. Magnesium anodes are the opposite of zinc anodes because they perform well in freshwater but poorly in brine. However, aluminum anodes can work well under both saline and brackish water conditions. Using aluminum in salt water is also more economical than using zinc, as under these conditions, the lifespan of aluminum is 50% longer than that of zinc. Therefore, it is rapidly replacing zinc products in many ship applications.

Aluminum is less toxic than zinc, and the activator used in aluminum anodes is less toxic than cadmium. So, you can see why aluminum is a better choice than zinc. Aluminum anodes are more economical, environmentally friendly and easier to use. Another advantage of aluminum is its lightweight. Aluminum is one of the lightest yet strongest metals available, so it adds very little weight to your boat. However, aluminum doesn't work well in pure fresh water.

Deyuan Marine aluminum anodes are fabricated as per the standard of GB 4948. If necessary, CCS, BV, ABS class certificate can be provided.

With the features of light weight, high capacity, simple and economic, Aluminum Anodes were widely used for Hull, Ballast tanks, offshore engineering, harbor structures, sea water cooling system, and submerged pipelines.

Deyuan marine offer a variety sizes &shapes of Aluminum Anodes for option, OEM service also acceptable.

For any new demand, pls feel free to contact our sales team for further discuss.