Hello,A long shot, but maybe someone can help.We have encountered two instances of seawater-cooled tube-and-shell heat exchangers with severe pitting on the inner surface of the tubes localized at the baffle positionOur findings were confirmed by videoendoscopy.My educated guess would be that the stress at these locations is causing the passivation layer to fail, but one of the exchangers is treated with ferrous sulphate to prevent erosion-corrosion.It's a mystery, and I have been unable to find any such instances in literatureYour comments would be appreciated.
Consult your friendly neighborhood metallurgistDepending on the quality of your endoscope images, someone skilled in seawater corrosion can probably tell a lot just by looking There are many types of corrosion and the causes varyIf it is near a baffle, you might be getting cavitation which damages the corrosion coating or, if there are abrasive particles circulating, it might be wear, if the velocity is low, sediment may settle there and create conditions for bacterial activity that damages the coatingIt is also possible you have poor quality metal and there is a microstructural basisSame as most engineering problems, the issue is determining the trade-offsIs it better to run until corrosion causes failure and replace the failed tubes or change the operating conditions (reduce water velocity maybe) or add cathodic protection? good luck
paper cup decorated / colored / made to look special by the kidsl; you have an ugly one can be cut up / smashed upPull a paper out of your cup with a bad situation, and the usual bad responseexample You have to eat leftover meatloaf for the second day in a row and you usually say again which makes your mom feel bad Then ask how it could have been saidReward with halloween treat into their cup.
