I was doing a survey in an underground hydro power station and had to abseil down into a cavern that nobody had visited in 15 years. there was a walkway with carbon steel safety hand rails that had an unusual form of corrosion attached which i had not come across before. There was a kind of crystallization occurrence with the crystals looking like shell found on a beach and being filled with liquid (presumably water). Can anybody help me with identifying this reaction please??