Hi Mark,
I would suspect that corrosion beneath this coating wasn't the fault of the coating per se, but was instead due to either faulty preparation of the steel deck plates prior to laying the Litosilo, which would be an application red lead primer and paint, or some sort of tar-based paint or coating, or from some undetected leakage finding its way beneath the flooring laid over top of the Litosilo. For anyone unfamiliar with Litosilo, it was a lightweight magnesite fairing, insulating and sound-deadening compound that was troweled over the steel deck plates and then floated smooth, providing an even surface over which linoleum, wood parquet, or rubber tiles were laid.
Litosilo was not a waterproof material, nor was it capable of providing a durable walking surface that could stand up to foot and other traffic, so it was always laid as the undercourse beneath linoleum or some other hard flooring, and was used only in compartments that weren't subject to anything more in the way of moisture than a good mopping. In bath rooms and WC's, and in spaces like the galleys, where the decks were expected to become wet at times, ceramic or porcelain tiles were laid down over a bedding of Portland cement, which was far more resistant to absorbing and holding moisture.
If there was a problem with corrosion being discovered beneath the Litosilo, I suspect that it was either due to this substance being used improperly -- laid beneath a bath room or deck pantry floor, for instance -- or because there was persistent leakage of water from some adjacent "wet" location finding its way beneath the flooring of a Litosilo-treated deck. Such sources of leakage could be improperly caulked bulkhead coamings and deck bars around galleys, lavatory compartments and deckhouses, or from improperly caulked gunwale bars or angles that bordered waterways present in certain lower deck areas. Water which found its way in through any such deficient caulking would eventually be absorbed by the Litosilo and, through capillary action, would spread out considerably past the point of leakage. Especially when you consider that sea water was used for deck-washing, bathing and sanitation purposes, the potential was always present to create a serious corrosion problem should this water find its way past the coamings which separated the "wet" spaces from the Litosilo-laid decks of the surrounding accommodation area.
Regards,
Scott Andrews
