Cleaning Mild Tool Steel

Q. How should I clean mild tool steel tablet press punches and dies?

A. Mild tool steel, sometimes called S7, will flash rush during rinsing, particularly if you rinse with hot water. All Alconox Inc. cleaners that have good chelating agents (all save Luminox® Low-Foaming Neutral pH Liquid Detergent and Detergent 8® Low-Foaming Ion-Free Detergent) can safely clean tool steel because the chelating agents tie up the iron oxide and do not let it autocatalytically expand and form rust. Once these are rinsed away, the dissolved oxygen in the rinse water will start rusting – faster with hot water. It is risky to cool tool steel with aqueous cleaners. The best way to do it is to rinse quickly with cool water and then dry as quickly as possible using a water removing technique (dipping in isopropyl alcohol, blowing off the parts, wiping off the parts, etc).

If you evaporate the rinse water dry, you will almost certainly get rust during the evaporation process. This process seems to be worse with DI or purified water than tap water, although for pharmaceutical punches and dies, you are often required to use purified water to clean with. The very best option is to use chrome coated tablet press punches and dies, which are easy to clean and you do not need to worry about rust (unless the chrome coating gets scratched!!!). In general I like to recommend Citranox® Liquid Acid Cleaner and Detergent or Alconox® Powdered Precision Cleaner  (Liquinox™ Critical Cleaning Liquid Detergent if need be, although the phosphate in Alconox powder is a better corrosion inhibitor during cleaning) based on if the contaminating residues to be cleaned require an acid or an alkaline cleaner for manual or ultrasonic cleaning of punches and dies.

To test these or any Alconox, Inc. detergent for free, please complete the questionnaire at Get Sample.