STATION 9. Cold Water Rinse The principles of operation for the nitric acid rinse are essentially the same as those for the other acid rinses. The main difference is that nitric acid solutions are generally much easier to remove by rinsing than alkaline residues or electropolishing solutions, and lower flow rates and/or shorter rinsing times may often be used. It should be noted that drag-in of nitric acid to the following hot water rinse may cause staining of the parts in storage. Therefore, some care must be taken to ensure that the acidity is not permitted to reach excessive levels in Station 9.