After the boiler is outage,  if the pipe inner surface is moist,  the outside air will enter and will cause  oxidation corrosion of inner surface .In order to prevent the occurrence of this kind of corrosion, the boiler shall be maintained after the boiler is stopped. For different boiler shutdown, there are several maintenance methods as follows:
1. The steam pressure method is used for anticorrosion. If the boiler standby time shall be no more than 5 days, this kind of method can be used.
2. Water overflow method of corrosion protection is used for that when the boiler is stopped for standby, or the non-bearing defects are treated, the downtime is in 30 days or so. During corrosion protection, special persons  shall be designated for monitoring and maintaining the steam drum pressure within the specified scope, in order to prevent excessive pressure changing.
3. The ammonia liquid corrosion. If the boiler standby time is longer,  this kind of method can be used.
4. The drying method of boiler waste heat. This method is suitable for the protection during boiler overhaul period.
5. The desiccant method. This method is used when the boiler is required to be in long-term standby.（lsh）