Removing Sand Residue from Casted Parts: Cleaner Selection Is Critical

Surface finishers are continually challenged with selecting the right cleaners to remove sand residue on casted parts. The main reason for this is that sand — typically a silicon-based compound— is insoluble in water, which causes the detergency of the cleaners to be lost.

Detergency is what allows the cleaners to pull soils into the solution and remove them from the part’s surface. The sand (or silicon) itself does not affect the detergency of the cleaner; it simply isn’t acted upon by it. With sand residue, good solution movement is critical, as you must rely on mechanical forces to remove the sand.

So how do we get good solution movement? I am personally a fan of eductors. They work by generating a jet action under the surface of a liquid. This can cause tremendous solution movement, and often works well for knocking the sand off of parts. However, it must be stressed that balancing the solution movement is key. If your parts are too lightweight, or aren’t on the rack securely, the solution movement may knock them off the rack. Too little and the sand won’t be removed.

Furthermore, you also need to monitor potential sand buildup in the cleaner solution. The easiest way to observe this is to pull a sample of the cleaner in a glass beaker, and let it sit on the counter until it has cooled and settled. If you see sand sitting on the bottom of the beaker, you can be sure that there is sand throughout the bath. You are then left with a few options for dealing with the sand in the bath, including:

  • Let the entire tank settle and cool, and then decant the liquid off and vacuum or shovel the sand out of the bottom of the tank.
  • Run the bath through a filter. Be extremely aware that this method would likely remove surfactants from the bath, and may necessitate that you make add backs.
  • Dump the cleaner and make it up fresh.

The method chosen will likely be dictated by the amount of work you are putting through the bath. For example, high volumes of work may make it uneconomical to dump the bath or filter it. Time constraints should also be strongly considered. While all of the methods for controlling the amount of sand in the bath have a time requirement, some will be quicker than others. Decanting is likely the most time intensive, but likely the least costly method in terms of chemistry. Dumping the entire bath and making it up fresh is likely the quickest, but most costly. Filtering will probably be somewhere in between for time and cost.

Given all the variables to ensure reliable cleaning performance on casted parts, I encourage you to contact your local Asterion engineer. We look forward to working with your team to deliver high performance and consistent cleaning results.