Galvanic corrosion, alkaline acidic corrosion, and stress-corrosion cracking have all been known to happen in certain conditions. Here are ways to reduce attack.
Although the extent and resultant cost of corrosion under insulation (CUI) are not known exactly, J. F. Delahunt in "Corrosion Control Under Thermal Insulation and Fireproofing" shows the seriousness of the problem by presenting case histories. These cover deep pitting, as well as general corrosion, that have occurred on galvanized steel tanks under 12-year-old polyurethane foam.
Delahunt advises that metal loss can be the least of the problem. For example, an eight-inch carbon steel pipeline carrying heavy fuel oil was insulated with calcium silicate block and protected with a metal weather jacket. The pipe corroded, resulting in a leak. The oil was ignited and a large fire ensued, causing hundreds of thousands of dollars in damage to process equipment.