STATION 4. Cold Water Rinse The principles of operation for the acid descale rinse are essentially the same as those for the alkaline cleaner rinse. The main difference is that acidic solutions are generally much easier to remove by rinsing than alkaline residues, and lower flow rates and/or shorter rinsing times may often be used. It should be noted that drag-in of fluoride and nitrate ions to the electropolishing bath may cause etching and/or pitting. Therefore, some care must be taken to ensure that these ions are not permitted to reach excessive levels in Station 4.