DIY underwater corrosion meter...zinc reference cell? silver?...?

[EngStdntANDDiveBus]

I am a freshman(mech eng) and owner of a dive company(pleasure
craft hull cleaning) I am trying to improve my service by
building a meter to help pin down and quantify corrosion issues on the boats i service.

So far I am clear with a waterproof multi-meter and a probe.
The foggy part is what to I put on the black/NEG lead.....
Will a sealed wire with a fused ball of anode zinc work?
Whould anode aluminum be better? More mass the better?
more surface the better? Won't matter much?

"silver/silver chloride half cell" seems to be the professional way. Any ideas about what kind i would
want to buy??

I just paid my tuition so this project is low budget as of
now. I will wait if needed but I kinda suspect knowledge
is needed more than money.

WHAT EVER WISDOM IS APPRECIATED GREATLY
SCOTT

ps: attachment is a above water version

 

[fdac]

You can buy these commercially, "Bathycorrmeter" or similar. A piece of sufficiently pure zinc would theoretically work, but to be useful it would require calibration against a 'real' reference electrode.

 

[jackthebear]

Scott-
Here are a couple of sources;

http://tinyurl.com/ygs8kbw

http://www.boatzincs.com/corrosion-reference-electrode.html

Why do you think you need a waterproof DMM?

Charlie

 

[ssm23671100]

I have a problem with corrosion not in seawater but fresh water.the 10mm bottom plates on the narrow boat as pitted from stem to stern but the bow plate which is welded to the corroded plates shows no sign of corrosion.I have had ameterlurgical annalasis done.this shows the bow plate came from a differant batch,but the only significant differance is the manganese contentwhich in thegood plate is 1.08%,and the bad plates 0.48.Any ideas would be gratefully received.

 

[cloa]

ssm23671100- You should start a new thread.