Here is a simple truth “Nothing gets Plated until it gets Cleaned” Despite this simple truth, cleaning is often a neglected part of the metal finishing process. Here are some basic principles in metal preparation to follow to help you determine how well prepared the parts are in subsequent plating or finishing operations.
Soak Cleaning Fundamentals
Soak cleaners are used in simple tanks in which parts are immersed and then left to sit for a period of time. Typically soak cleaners are controlled by time, temperature and concentration. Used properly, soak cleaners should remove all of the oils or buffing compound on parts.
Soak cleaner life is directly proportional to soil loading. Soil load split tests are run to determine the quantity of soil that is present in the cleaner tank. These test are used as an indicator to determine if the soak cleaner should be dumped and recharged. Another metric used is to calculate the approximate work processed (sq ft or part total) since makeup.
A common error made in the use of soak cleaners is to change them based on a tiem schedule regardless of soil load or square footage processed. This time based cleaner schedule often leads to failed cleaning that could easily be avoided with proper tracking and testing.
A few more notes about soak cleaners. Water emulsifiable soils are readily removed in mildly alkaline, lower temperature cleaners rather than a strong, hot cleaner. Many finishers utilize a warm water prerinse prior to the soak clean tank to economically remove these oils.
Non-emulsifying or cleaners that float in the oil is also common. These cleaners release the oils to allow for oil separators to remove the oil from the top of the solution. The oil is then captured and sent out for disposal. Another method finishers use is to allow the cleaner tanks to cool and the oil is released to the top of the solution.
Electro Cleaning Fundamentals
Electro cleaners are exactly what they sound like. Electro cleaners are used in tanks that parts are immersed in and left to sit for a period of time while electricity flows through the solution. Typically electro cleaners are controlled by time, temperature, electrical current and concentration. Electro cleaners are not designed to remove large quantities of oils or other organic substances. Their key objective is to remove particulates (i.e.- smut, etc) from the parts through gas scrubbing; either through Anodic (“reverse”) or Cathodic (“direct”) cleaning.
However, Periodic Reverse (or PR) cleaning can be used as an effective descaling method. Direct cleaning provides double the gas scrubbing action as in reverse cleaning. It is set up the same in polarity as a plating cell where work is negative (-) and the cathodes are positive (+).
Electro cleaners can make a huge difference in quality of plating. But the quality of cleaning really depends on making sure the cleaner is properly maintained. If the solution is dirty or contaminated (i.e.- metallics, etc) these contaminants can be redeposited on the parts which will often leads to adhesion failure in the subsequent plating process. Your chemical supplier should be helping you make sure that your electrocleaner is properly made up and properly maintained.
In plating success is neither magical nor mysterious. Success is the natural consequence of consistently applying the basic fundamentals from the first tank of your line to the last. For help reviewing the fundamentals of cleaning parts on your line please contact your local Asterion representative.