A deionized rinse uses water stripped of dissolved minerals, usually checked by conductivity in microsiemens per centimeter. Soluble salts left on the part after drying pull moisture through the cured film and cause blistering and underfilm corrosion. Many specs require the drip-off from the part to stay below a set conductivity, and thin-film pretreatments depend heavily on clean DI rinses.
Drip-off conductivity is up to 60 on the last stage, swap the DI bottles before we start blistering.
A rising conductivity reading at the last rinse is the early warning for blistering that will not show until the parts have been in service for months.
Also heard as
- deionized rinse
- DI water rinse
Related terms
Seal rinse
A final pretreatment rinse that fills pores in the conversion coating and boosts corrosion resistance.
Thin-film pretreatment
A zirconium- or titanium-based conversion coating only nanometers thick, run in place of phosphate on many lines.
Five-stage
Shop name for a spray washer with five tanks: clean, rinse, conversion coat, rinse and final seal or DI rinse.
Pretreatment
The cleaning and chemical conditioning a part gets before powder, which decides most of its adhesion and corrosion life.