Protective system for underground pipes

In a method of protecting underground pipe from corrosion in a region in which the pipe extends through a casing in which water has collected and may be subject to the deleterious action of the collected water, including any destructive agents contained therein, comprising the steps of sealing the ends of the casing to provide a closed chamber around the pipe, and pumping a corrosion-resistant compound into said chamber to subtantially fill said chamber with said compound and simultaneously displace all or much of the water from said chamber, the improvement comprising introducing to said chamber, prior to pumping the corrosion-resistant compound thereinto, a treatment substance capable of mixing with the water and reducing or neutralizing its deleterious effect so that any water remaining in said chamber after the corrosion-resistant compound has been pumped into said chamber will be relatively harmless to the pipe.