When companies realised that a new market was emerging a quick fix was found and marketed in the Ceramic coating markets to insulate shipping container homes in reality it was fake. In fact the information they used to justify the Ceramic coatings being used couldn’t be replicated and on top of that you could pretty much get the same result using white paint which is a lot cheaper and easier to find. In reality the best method is SPF insulation (Spray Polyurethane Foam) which is a sticky mixture that fills the voids easily creating a solid wall of foam. I would recommend using this internally with stud partition that you panel over once insulated. Another issue people are overlooking is condensation which causes rust although its not as bad as people often make out due to the design of the ISBU which stands for “Intermodal Steel Building Unit.” It doesn’t rust easily its designed for some of the harshest environments on the planet and has not only got to deal with what the weather throws at it but also being thrown around. Its a solid piece of equipment and if treated properly is going to probably out last most people who convert over to the new modular way of living.