Chemical cleaning now has been applied to all equipment which contains scale and sludge deposits in central stations. A discussion is given of these various units along with a description of the different types of solvents employed. An explanation of certain types of corrosion is given. Improved acid corrosion inhibitors are now being used in order to give the necessary protection on stressed areas, on zones having dissimilar grain sizes, and on metals containing the Widmanstätten structure. Information is given as to the ferric-iron corrosion problem.