Choosing the Right Passivation Chemical for Your Parts

Passivation selection is a three-way trade between corrosion specification, appearance and cost per square metre. Getting it right starts with one number: the salt-spray hours your customer actually requires — to white rust and to red rust.

Match the chemistry to the spec

Up to 48 h white rust: trivalent blue is the economical default with a clean bright finish. 72–120 h: thick-film trivalent yellow. 120 h and beyond, or red-rust requirements past 400 h: add a silicate or polymer sealer over the passivate — sealers typically double or triple film performance for a few paise per part. Black passivates trade some corrosion margin for appearance; olive drab maximises film thickness for defence-type duty.

The mistakes that fail audits

Running passivate baths past their zinc-contamination limit, skipping the post-passivate rinse discipline, and oven temperatures above 70°C that dehydrate the film — these three explain most unexpected salt-spray failures we're asked to troubleshoot.

Unsure which system fits your drawing? Send us the spec line and current process; we'll recommend the least expensive chemistry that passes.