Corrosion can severely affect tablet compression tooling used in the production of animal medicine if it is not addressed effectively. It can delay production, reduce efficiency, and cause contamination problems. There are several reasons why corrosion can occur, and although challenging, it can be resolved with a combination of the correct tool steel selection, coating or treatment, and maintenance procedures.
Corrosion can be detected by the appearance of discoloration, etching, or common red rust. The main cause of corrosion is acidic substances that can include ingredients found within the formulation being compressed, and even in the surrounding atmosphere. The iron particles in the metal tooling are exposed to oxygen and moisture in the form of humidity or vapor. When the steel is exposed to water, the iron particles are lost to the water’s acidic electrolytes. This means they oxidise the iron particles which form corrosion on the punches and dies.
One of the principal causes of corrosion is excessive moisture and humidity. This is because corrosion often forms in areas where liquid is present. Oxygen is found in the air we breathe and humid air carries water. The percentage of water vapor in the air varies based on temperature and can range from as low as 0.2 percent to up to 4 percent water vapour1. Excess humidity in the compression room, tool storage area, or places where the formulation is stored prior to compaction can have a significant impact on corrosion forming on the tooling. It is therefore extremely important to control the environment in all areas of tablet production.
As we cannot remove oxygen from the air and tooling is made from steel, considerations should be in place if required to regulate the temperature and humidity, minimise moisture, and ultimately prevent corrosion from forming on the punches and dies.
All formulations have very different characteristics with varying moisture content, which is often needed to help bind the tablet structure. However, too much water within the tablet can be a cause of corrosion and lead to other problems like sticking with a rise in adhesive forces. It is not just moisture content within the formulation that can lead to corrosion. Formulations containing corrosive elements such as chlorine, salts, and acids will react with the tooling surfaces and result in oxidation.
Protecting Against Moisture
Optimising the tablet compression and tooling storage environments can have a significant impact on preventing corrosion, but other solutions should also be considered.
Tool Steel Selection
Granulates can contain corrosive elements which react with the steel. This reaction can lead to tabletting defects like black spots which are the result of corroded tooling and sticking where the granulation adheres to the punch tip face causing costly wastage, reduced yield, and unwanted press downtime.