Degreasing and phosphatizing during powder coating pre-treatment

Phosphoric acid, phosphate, surface active agents, oils/ lubricants

In surface treatment the rinsing water quality following a degreasing/Fe-phosphatizing is subject to high demands, as salt residues or traces of oils and surface active agents on the work pieces significantly reduce the absorption during the later varnishing or powder coating. Through the processing of the rinsing water with the VACUDEST® process, impurities such as salts, oil and surface active agents are safely removed and allow a constant high rinsing water quality to be achieved. Only via the VACUDEST® process with direct vapour compression is a germ free, desalted distillate available as rinsing water. The rinsing water is taken from the first rinse, distilled and directed to the last rinsing zone, i. e., demineralised water post-rinse nozzles. This creates a closed water cycle. To compensate for the evaporation losses water, from a reverse osmosis is added to the last rinse stage. Upon disposal, active baths can be processed in batch quantities with the VACUDEST® With a fluoride-containing phosphatization, a neutralisation is pre-connected to the distillation.

Practical experience in continuous operation shows that a 100% recycling and circulation process of the rinsing waters leads to optimal cleaning results. In applications in which there is an existing danger that traces of oil or surface active agents might be imported into the system via evaporation, VACUDEST®, can post-connect a combined gravitational coalescence and active carbon filter. The waste disposal of concentrate is < 1 %. This means that the waste volume is reduced by factor 100. The concentrate from the VACUDEST® can be directed back into the active bath, following the distillation of rinsing water, dependent on the chemicals used. The VACUDEST® process has proved itself in practice to be the most economical process in the treatment of rinsing waters from Fe-phosphatizing.