Dip tanks are a workhorse in the industrial application of water-based coatings. They are a tried, true and efficient method of coating parts of many configurations, but no method of application is without elements of preventative maintenance.
One such maintenance item required is to keep the coating properly balanced while in the tank. The top surface of the tank is exposed to air, allowing volatiles and non-volatiles (water) in the coating to evaporate into the atmosphere. These lost components must be replenished regularly, especially in slower tank turnover operations. There are three basic additions recommended:
- Virgin Coating: this is the primary addition you make to your dip tank and should make up the bulk of the additions. All the ingredients lost in the dip tank through evaporation are present in the virgin material. If you put enough virgin coating back into the dip tank, then the other additions can be minimal.
- Water: this is the second addition you would make to your dip tank. The viscosity of the coating can go up over time. The easiest and often best solution is to add water to the specified viscosity optimal to maintain proper application and coating weights.
- Amines: this is the tertiary addition made to maintain a proper pH and is vital to the coating’s stability. Unlike viscosity, the pH slowly goes down with time due to the amine, present in the coating, escaping into the atmosphere. This will also cause the Volatile Organic Compound (VOC) level to go down as well, which can lead to application and performance issues. Both considerations make it necessary to replenish lost amines and maintain the pH recommended by your supplier. A typical amine addition might be dimethylethanolamine (DMEA), but others may be used based on the formulation of the coating.
Although there are times when other additions are needed to overcome surface contaminants, film edge pull, or other film defects, these basic additions are fundamental to maintaining a healthy dip tank, maximizing application quality, and film performance.
We help our clients maintain their dip tanks through:
- Comprehensive operator training.
- WI-OP work instruction-operating procedures.
- Routine tank sampling to evaluate physical properties and gas chromatography (GC) analysis.
- Detailed reporting outlining necessary additions and performance to tank metrics.
Marcus Paint is dedicated to the success of each client — as well as our processes. Browse our informative blog content here, and read about our client challenges, solutions, and outcomes in our case studies here.