Sentence:  Corrosion of <WSD>pipes</WSD> leads to the release of soluble iron and lead. ... Corrosion control can be accomplished in distribution systems by adding compounds that form a protective film on the <WSD>pipe</WSD> surface, thereby providing a barrier between the water and the <WSD>pipe</WSD>. Although these corrosion inhibitors limit metal solubility or reduce corrosion, deterioration of the <WSD>pipe</WSD> surface is not entirely prevented. 
Meaning of the word marked with <WSD> tags:  A water pipe.