One of the most important and pervasive problems to overcome in marine engineering is corrosion. When exposed to salt water, many metals corrode rapidly. This can rapidly degrade their structural integrity and render boats and seaborne structures unsafe. Repairing corrosion is expensive. It often requires simply replacing the damaged component. There are some materials that do not corrode in the same way, but few of these are suitable for constructing anything of significant size. Their material properties tend to be unideal, and they tend to be expensive.

This makes CAPAC systems critically important. CAPAC is a brand name, but it consistently is used to refer to active cathodic protection systems. Cathodic protection is a means by which materials susceptible to corrosion can be protected from the constant assault of salt water, and whether or not you are conscious of it, almost all seafaring vessels rely on it. It relies on some simple scientific principles which will be explained here with a brief explanation of passive and active cathodic protection.

The most common form of cathodic protection is passive. This is seen mostly on small boats, and consists of nothing more than a “sacrificial anode” which will effectively corrode in place of the structural material. This works because it turns the protected material into a component in an electrochemical cell. The anode, while active due to its own corrosion, balances the electric potential of the protected material, and this effectively precludes corrosion on a chemical basis. For many larger structures and boats, this is insufficient. When a passive solution is insufficient, an active solution is used instead.

 

sacrificial-anode

 

 

Sacrificial Anodes Protection On Ship

Sacrificial Anodes Protection On Ship

 

Sacrificial Anodes Before and after Corrosion

Sacrificial Anodes Before and after Corrosion

 
Active cathodic protection relies on DC current. The anodes of a passive system work because they are capable of balancing the electric potential of the metal to be protected, but on a large scale it isn’t possible or economical to have a sufficiently-large anode. DC current can be scaled up much more easily, however. By forcibly passing DC current through the hull of a ship, the spar of a rig or some other metal structure to be protected, it transforms the whole device into an electrical circuit. This forces the electrical potential to stay uniform and prevents corrosion.

On a large scale, this requires a high standard of quality. Voltage and current levels must be maintained meticulously in response to changing conditions. Whatever power source the cathodic protection system relies on will need to be carefully regulated every step of the way, and even a change of temperature outside can demand a change in conditions. These are processes that are best automated and handled with precision; this is one of the areas in which CAPAC shines with their cathodic protection solutions.

If you are interested in active impressed current cathodic protection systems and the CAPAC brand, you can find more information here. Cathodic protection isn’t optional for any large-scale seafaring project. Whether you are protecting the integrity of a ship, an oil rig, a pipe line or a bridge, corrosion is your worst enemy, and cathodic protection is your sole defense.