Since a majority of powder coating systems today include a spray washer system, it seems appropriate to provide a certain amount of in-depth information on the maintenance of the pretreatment system.
Pretreatment failures are the single largest cause for rejects in the finishing industry today.
Unbalanced chemical concentrations, bad rinse water, clogged or misdirected nozzles, and other factors left unattended will certainly cause rejects regardless of the top coat quality. Rejects related to the pretreatment system can be reduced drastically with a properly implemented maintenance program. Aside from the daily, and in some cases hourly, titrations that are performed to determine the chemical concentration levels in each stage, the pumps, nozzles, and burners, will also need proper attention. The objective is to deliver parts with clean surfaces and with proper phosphate coating weights, to the powder coating booth as quickly as possible. A maintenance schedule and log book should be kept to track the regularity of the additions of make up water, chemicals, and replacement parts that are used in the pretreatment system.