So I strongly suspect it is down to the very high concentrations of very corrosive electrolytes (KOH and NaOH) that most people here tend to use. These poor electrodes are basically immersed in extremely strong acids or alkalines, which are then made more active by continuous ion current flow. Stainless steel is good, but its corrosion resistance has its limits! Not to mention the fact that if the metal is reacting like that, then the gas output will be reduced by non-productive chemical reactions.

To me this is just one more good reason to minimise the concentration of such electrolytic compounds.
Farra, there is lots to learn from these plates. Here are some. First, this is what happens to someone who does not know what they are doing. If you look carefully at the plates you can tell exactly what happened. I was told the electrolyte was 8% NaOH that is less than 50% max and ran at reasonable temps (just between 38º C to 40º C) drawing 8 to 12 amps. Now on a 2500 mile trip you would think one would consider adding water well in this case not until the amps moved up to 15 amps did this enter into his mind duh... This happened more than one time during the trip. You can see the electrolyte level was right at the high damage line so obviously it ran like that for some time. With the water being used up level goes down and concentration goes up causing increased amps in a very small area and the results are just what you see. This is a good time to recommend a PWM for people like this. I see a PWM as something to use in Winter when you are trying to keep the electrolyte from freezing 0º C or below and when it is linked to RPM/MAP/TPS to increase and decrease the amount of HHO being injected instead of just one amount all the time. Now this does not take into consideration pulsing etc to help separate the water into it's components which is still under investigation and not clear cut in the practical world anyway.