Yes I uderstand what you are saying, but what I was trying to point out to you is the fact that there are different types of corrosion cells, and I didn't mean stronger or weaker when I used the word different types of corrosion which are unique to power plant situations like inside boiler tubing where certain types of pitting, or erosion & caustic corrosion situations can only be found in a boiler of the types which are found in power plants as well as unique yet similar types of corrosion cells where the results of the same type of corrosion may be different based on either the type of boiler being used, or the fuel being used to heat them as well, and then there is the design factors as well that need to be taken into consideration such as the materials and the variety of components found in a utility boiler which will be different than what is mostly found in boilers used in chemical plants, pulp paper plants, process refinery plants as well...
There's a whole bunch of corrosion going on in the anti pollution devices found in utility plants that have been replaced more than once already since their initial installations as well which really doesn't get mentioned that much either, but I'm not going to get inot that here because that's a whole different animal all together. ;)
So water formed and steam formed deposits are quite common in utility boilers that originate from other areas of the boiler that are causes of corrosion, as well as from both short term and long term overheating which deos play a role in accelerating the creep potentials at various locations in the tubing/piping along with other components as well, then there's the clogging of the superheater tubing which can vary widely in the types of deposits found that eventually lead to clogging these pipes completely eventually causing them to bulge then rupture at a variety of locations and resulting in catastrophic failure more often than usually reported!!! ;) Of course there's also Water wall fire side corrosion which occurs in boilers no matter where they are used.
Then there's the usual caustic, and chelant corrosion cells that from over time as well as low Ph service corrosion as well as during acid cleaning also. Then of course there's the uniqueness of oxygen corrosion in far higher levels in utility boilers than would be found in chemical plants or process refineries too. But what is really unique about utility boilers or even some paper mills would be the coal ash type of corrosion, or the oil ash corrosion like from black liquor in the paper mills which is why a lot of duplex SS cladding was addded to these black liquor plants in the seventies in order to mitigate some of the oil ash corrosion found in a variety of locations and on many different components.
Then of course there's cold end corrosion during service as well as dew point corrosion during idle periods... Hydrogen damage, materials deficiency cavitation, dealloying, graphitic corrosion, corrosion fatigue cracking, stress corrosion cracking, etc. In other words, all of these corrosion environments and situations and unit cells occur in boilers both in utilities as well as in chemical plants but, certain corrosion cells form uniquely in a utility boiler, yet do not always mean that one is stronger than the other because that was NOT my point! My point was that there are certain corrosion cells that occur only in utility type boilers and NOT found in boilers found in chemical or process plants with the exception of the black liquor fuel used in a paper mill, meaning that the fuels used to heat the boilers are an important factor as to why some of these unique corrosion cells even form at all in a utility plant as opposed to a different type of boiler used in a chemical plant which more than likely would be using natural gas of some sort to heat the boiler up to produce the steam from the water running through those tubes/pipes - CAPECHE??? In other words, the B31.1 part of the system in a power plant... So I hope I clarified what I was initially attempting to point out to you previously Giovanni! ;)