It is well known that metals annexed to leathers are easily corroded and various kinds of troubles come from this corrosion. However, the reasons for this corrosion have not been clarified. The present study has been made only for chrome-plated steel pipes. In the corrosion of steel annexed to leather, chloride ion eluted from leather is considered to be the main factor for the corrosion except in a few cases. In addition to chloride ion, eluted sulfate ion is thought to be the secondary factor although its effect on corrosion is relatively weak. There were some cases where no corrosion was observed although much chloride ion was eluted. This may be explained by the fact that there is no contact between a steel pipe and eluted chloride ion due to limited water vapor permeability of a leather surface in contact with a steel pipe or there is a painted surface on a pipe. If a different kind of metal is annexed to leather, different kinds of eluted ions may be considered to be responsible for corrosion of the metal.