After phosphating, a dilute final solution fills gaps between phosphate crystals and passivates bare spots. Most lines run non-chrome organic or zirconium seals rather than chromium-based ones. A good seal can add hundreds of hours in salt spray to an iron phosphate system. It is applied as the last chemical stage, often followed only by a DI rinse.
Salt spray panels failed at 300 hours, check if anyone has been dosing the seal rinse.
Also heard as
- final seal
- post-rinse
Related terms
Iron phosphate
A thin, amorphous phosphate conversion coating on steel, the economical standard for indoor and light outdoor parts.
DI rinse
Deionized water rinse, the final stage that washes salts off the part so they do not end up trapped under powder.
Five-stage
Shop name for a spray washer with five tanks: clean, rinse, conversion coat, rinse and final seal or DI rinse.
Salt spray
An accelerated corrosion test that holds scribed coated panels in a warm salt fog for hundreds of hours.