Quantitative based on the salt content which provides the basis for electrolytic action is as follows:<br><br>Sea Water 35,000<br>Lake Michigan 170<br>Rivers 360 - 2600<br>Rain 10<br>Distilled 0<br><br>However, any rate of corrosion has to be based on material (polymer, metal, etc.), its composition (NI-AL-BRZ, Zinc, etc.) and whether it is in contact with other materials (galvanic corrosion), etc.