Caustic attack, explained.

Caustic attack gets described as corrosion, which is close enough to be useful and wrong enough to lead people to the wrong fix. What is happening is chemical: the liquor works into the matrix, reacts with the bonding phases, and the lining loses the thing holding its aggregate together long before the aggregate itself is in trouble.

That is why a lining under caustic attack often looks sound from the outside and comes away in handfuls when you touch it. The wear face is not being abraded away, it is being converted, and the strength goes first.

The practical consequence is that hardness is the wrong thing to specify against. Permeability and bond chemistry matter more, because the mechanism is transport into the matrix rather than loss at the surface.

Every lining lives in a set of conditions before it lives in a vessel: the chemistry it meets, the thermal cycle it rides, the abrasion it takes at the wear face, and the access the crew gets when it is time to put a new one in. Change any one of those and the right answer moves.

What we look for is the point where the decision was actually made. Usually it was not on the shutdown floor. It was in a specification written months earlier, against an assumption about service conditions that has since moved.

It also means inspection needs to change. A visual check of the wear face will not find this early. A probe, a core, or simple hammer sounding will, and doing it on a schedule turns a surprise failure into a planned replacement.

If you are working through this on a vessel of your own, the fastest way in is to bring us the conditions you run in — cycle, chemistry, access, and what failed last time. That is enough to have a real conversation about what to change.