At a guess I would think it should be a non-issue. Plenty of people out there have run water injection on engines. Makes no difference (corrosion/wear wise). If anything running water injection helps get rid of carbon build-up in the combustion chamber and exhaust valves. Think of steam cleaning something. Appearently on the tear down of water injected engines, the combustion chambers are as clean as a whistle.
Now, granted, this isn't a water injection setup. The Oxygen and the Hydrogen are seperated at the begining, but they are being recombined into water, so I should think the end product is similar. If anything I wonder if that is where the cylinder cooling claim is coming from, possibly. Water has a fairly high thermal mass, so it suckes up alot of the heat from the combustion process, flashes to steam (which if I remember correctly has expansion rate of like 1600 times - say you had one cubic inch of water and flashed it to steam, it would now occupy 1600 cubic inches) which in turn helps push the piston.
Or I could be completely wrong, because I have no idea how the extra O's and H's are going to react to the rest of the combustion process. Chemistry was never my strong suit but, I would like to see a bit more detailed explanation of what is actually happening in the combustion chamber.
I guess my problem is with this statement:
"Adding a moderate amount of Hydroxy gas to a gasoline or diesel engine, can radically change the rate of combustion in the cylinder. It accelerates the rate of combustion of the primary hydrocarbon fuel (Gas, Diesel, Ethanol, etc). This leads to more pressure on the piston on the power stroke so there is more torque, less heating of the block, and less unburned hydrocarbon fuel going out the exhaust port."
No offense, but last I checked, we really don't want to speed up the combustion process because that is what happens in detonation. A proper air/fuel ratio in a combustion chamber at the proper temperature *burns* rapidly and smoothly pushing down nicely on the piston. When it gets too hot (either through compression or a hot spot in the combustion chamber) or the A/F ratio goes too lean, the mixture detonates and literally explodes which is too sudden of a shock for the piston and rotating assembly. This is why we have higher octane fuels. To raise the ignition point of the fuel when need be.
Also it would seem by your statement that somehow by adding this extra fuel to the combustion process raises the pressure of the combustion event, but does not raise the overall temperature. That would seem to be a direct violation of Charles's Law. For a given volume, if pressure goes up, the temperature goes up. Simple as that. Heck, that's how a diesel engine works. Compress the snot out of A/F mix until it heats up to a point where it ignites on its own. No spark needed.
However. In the case of the water injection, volume goes up, pressure goes up, but the water is being used to absorb the heat - since it is not actually being combusted, less heat is transfered to the cylinder and combustion chamber. Walks like a duck, quacks like a duck. I'm thinking its a glorified water injection system, but I could be wrong. As is frequently the case.
As to Lee's comment about added system ineffiency - Maybe I misread it, but during one of the discussions a while back on the operation of the electrical supply system, basically it generates full power all the time, and sends left over to the R/R to be turned into waste heat anyways. If that is right, he would just be using potentially wasted energy anyways. Kind of like running a turbocharger as opposed to a supercharger.