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Marine Corrosion Explained, please contact us if you continue to have any questions.

Frequently Asked Questions: Marine Corrosion Explained

Marine Corrosion Explained

Marine corrosion is estimated at 4% of the Gross National Product. The facts listed below will encourage marine designers, engineers, and equipment users to consider the options for using protection and corrosion control to reduce the high maintenance costs of aqueous corrosion.

There are many types of destructive corrosion which can occur to boats, ships and other marine equipment used in sea water service. Aqueous corrosion causes the most problems we encounter in sea water activity, however atmospheric corrosion near coastlines, and sea water splash are equally troublesome and require corrosion control products to eliminate or control them.

Corrosion by Sea Water

Corrosion by sea water is an electrochemical process, and all metals and alloys when in contact with sea water have a specific corrosion potential at a specific level of sea water acidity - the pH.

Although there are corrosion resistant metals such as gold platinum and tantalum, these are rarely used in the marine industry because of the high costs involved. Most metals used today are susceptible to the damaging effects of aqueous corrosion.

The metals used in the marine industry most likely rely on an oxide film to provide corrosion protection. If the film is applied correctly, then the metal will be highly resistant to corrosion. However, in most cases, the film is loose and easily damaged causing corrosion on the exposed and unprotected metals. In the event that the film is applied correctly, in time, the metal becomes damaged because of the aggressive atmospheric conditions that the marine vehicles and equipment undergo.

Sea water is a most efficient electrolyte. The presence of oxygen in marine atmospheres, sea spray at the water-line, and sometimes at much greater depths, increases the aggressiveness of salt attack. Corrosion, in most cases, will begin in crevices. Crevices, which allow entrance of water and chlorides and not oxygen, rapidly become anodic and acidic creating starting points for marine corrosion.

Other factors can worsen the already problematic situation, microbiological organisms, accumulation of weed, limpets as well as deposits of sand, silt or slime not only leave out oxygen but often create a concentration of corrosive conditions under these deposits which increase significantly the corrosion problem. Bacteria, left undisturbed in marine silt or mud deposits, will produce concentrations of hydrogen sulphide which are particularly aggressive to steel and copper based alloys.

How can Aqueous Corrosion be Controlled?

There are five main methods for controlling the tendency of metals to corrode in sea water:


Separating the corroding metal from the sea water by using a protective coating, such as paint


Changing the potential of the metal to cease corrosion - by impressed voltage or coupling to a sacrificial anode


Making the metal passive, using aqueous corrosion control products


Changing the pH of the local environment by chemical dosing


Making a change to a more corrosion resistant material

Resolving the corrosion issues by method #3, by using corrosion control products, can most likely be the best and least expensive solution to prevent the damaging effects of aqueous corrosion. Using corrosion control products, such as Rustblock Marine, may effectively prevent attack in bilges and other areas where sea water will collect and stagnate. The Rustblock Marine team also offers technical support in preparing a reliable maintenance program to monitor and maintain the correct concentration of the corrosion control inhibitor products, which is an essential aspect of this prevention strategy.

Marine Corrosion can be Prevented

Key factors in prevention of marine corrosion are design, selection of materials, construction, use and and effective maintenance program. Ignoring any one of these may lead to a total failure to prevent a corrosion attack on your marine vehicle or equipment, which once started may cost far more to correct or eliminate than any savings on materials achieved at the outset.

In a recent survey corrosion was found to be responsible for 30% of failures on ships and other marine equipment.

Where to get Help

The Rustblock Marine Team is ready to prepare a customized solution and maintenance program to marine designers, engineers, and equipment users. Samples of our products can easily be ordered by just visiting our contact page or calling us directly on our North American Toll-Free Number.

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