Corrosion & Erosion Flashcards
Corrosion & Erosion: Types?
Corrosion & Erosion: Chemical corrosion
Corrosion & Erosion: Dry Corrosion 1
Corrosion & Erosion: Dry corrosion 2
Corrosion & Erosion: Galvanic corrosion
Corrosion & Erosion: Wet corrosion, Anode & Cathode
must draw
Corrosion & Erosion: Anode & Cathode & Greater Anode
must draw
Wet Corrosion: Dissimilar Metals
Wet Corrosion: Sacrifical Anode
Wet Corrosion: Galvanic corrosion 2
Wet Corrosion: Impressed current system
Crevice Corrosion
Crevice Corrosion 1
Crevice Corrosion 2
Fretting & Stress corrosion
Cavitation
Osmosis
Osmosis:
FRP construction can be damaged by Osmosis. This is seen by cracking or blistering of the
surface. Gel coat damage allows water to come into direct contact with the resins which
are porous and allow water to be ‘sucked’ in. If the resin is damaged, it must be replaced
before repairing the Gel coat. Cheaper FRPs use a polyester resin in the mix which absorbs
and produces water creating an acidic mixture. This may collect in small gaps in the layup
caused by bits of grit in the mix. This increases the pressure in these gaps forcing the
laminate apart and breaking up the FRP. High quality builds using non-polyester resins will
cure fully without absorbing more water.
Impressed Current System
Impressed Current System:
If the Galvanic Current can be suppressed, the corrosion can be stopped. By measuring the
current flowing and creating a reverse current from the ship to a cathode (or, in fact, a
series of cathodes) on the outside of the hull. This is only effective if the current is
constantly monitored and adjusted so the system must be controlled by a computer.
