Most process plants use substantial amounts of water. The water comes from a range of sources such as rivers, lakes, wells and oceans and contains dissolved and suspended solids. To reduce consumption, most plants reuse water; this, in turn, causes it to be highly concentrated in silicate, iron and calcium carbonate that prompt limescale build-up and rust.
Limescale deposition results in the need for regular shutdown to remove the build-up. Sometimes, this removal can take place as part of a planned maintenance program but, on other occasions, severe or even complete blockage by limescale can force unscheduled equipment outages until the blockage is cleared. In addition, scale deposits can increase corrosion due to entrapped oxygen and the scale itself sometimes can corrode the surface it contacts. Also, scale will interfere with the action of inhibitors in the system, keeping them from reacting with the surface below the scale. If the scale is patchy, the differential aeration between the clean surface and the scale surface may cause a corrosion cell to set up.
To learn more about preventing rust, read “Prevent Rust Formation in Pipes” from Chemical Processing.
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