In case of a pre-commissioning or post-commissiong cleaning, a boiler will often be decommissioned for an extended period. During a new construction project it could be that, due to circumstances, there is a substantial delay between finishing the construction and the start of the chemical cleaning. A long shutdown period is often chosen with older boilers, in order to check all the ancillary installations for wear and the like. If such is the case, it could be that the boiler will have to be decommissioned for a longer time after the chemical cleaning. In these cases a fitting preservation of the boilers will have to be considered, as in time corrosion problems will occur in the internal parts of the boiler due to the action of oxygen. Consider here the most important parts of the boiler.