Protect yourself with genuine anodes

Sacrificial anodes protect the metal components of outboard and sterndrive motors from electrolytic corrosion caused by saltwater and many regions of freshwater. They are designed to literally "sacrifice" themselves to protect expensive engine and drive components from corrosion.

"We're concerned that some boat owners will replace their genuine anodes with cheaper brands without really understanding the risk they are running," said Ron Bell, Mercury Marine's quality assurance manager.

"For example, many people don't realise that zinc anodes which are so common, have to be manufactured in virtually sterile conditions. Any contamination in the metal eliminates all of the zinc's sacrificial properties which means your engine will corrode instead.

"Genuine anodes have come through a high-quality manufacturing process. Have the others? It's a big risk for a few dollars," Bell said.

Furthermore, modern drive units are made of a range of metals - including lightweight aluminium alloy, hardened steel and stainless steel - which all have different reactive and corrosive properties. Anodes also have to complement all the other anti-corrosion processes Mercury applies to its drive units, like its EDP paint process and XK-360 alloy.

So considerable development and testing is required to produce the ideal anode, said the company Mercury said it has developed an aluminium alloy that provides better protection and lasts longer than zinc, but it has a lower mechanical strength making zinc anodes still preferable in some cases.

Anodes can corrode surprisingly fast, and should be replaced when they are 50 per cent consumed to ensure adequate protection. At its best, corrosion is expensive and inconvenient. At its worst, it leads to engine or drive component failure at sea, said Mercury Marine.

A corroded prop or lower unit is inefficient - resulting in lower top speed and fuel efficiency, and increased engine wear. Excessive corrosion can lead to equipment malfunction.

Mercury Marine said to not rely on experience when it comes to replacing anodes, as the speed of corrosion can alter if conditions have changed.

For example, Mercury Marine said corrosion rates will alter if: additional metal elements have been added like steering aids or trim planes; plugged into onshore power; there is a minor power leak onboard; moored near another boat with a power leak; the boat's paint is damaged; and, you've been in different water - salinity level and/or speed of movement.

If you have a Mercury, Mariner or MerCruiser engine then your Mercury dealer will be able to provide you with a marine corrosion protection guide.

For more info, visit www.mercurymarine.com.au