[I was] on the "Mimosa" in the summer of 1991,
when we ran into heavy seas at south tip of Africa.
We were fully loaded on the way to Rotterdam when this happened.
First we had a steering gear break down.
This was a Hastie type steering gear.
A non-return valve in the valve block between the two cylinders cracked,
the pipe connected could not take the pressure,
the pipe went out of its screwed socket
and, since the non-return valve was flawed,
all oil the system went on the flooring.
Hence the rudder slammed from side to side as the outside sea would drive it.
The noise and the speed with which the rudder
went from side to side was tremendous.
Finally, the port cylinder of the steering gear broke into pieces.
The starboard cylinder seemed to stay in the same position after this,
and we managed to some how secure the cylinder in a fixed position
with everything we could find of chain blocks.
Then we sealed off the steering gear room.
The bridge was then able to go dead slow astern for some 12 hours,
and we went in a circle in the hurricane.
This probably saved us from ending up on the South African rocks.
After 12 hours, there was a loud bang from the steering gear room,
and the rudder was "free" again.
By then the seas had subsided and we got tug boat assistance.
When it was safe to go out on deck,
we saw the 340 sq.meter hole in # 5S(ballast tank).
The shell plate was nowhere to be found.
And yes, corrosion did play a major role in this