Scope of this guide
Intermediate version: symptom-to-cause triage with the confirm-by column — find the variable, run one change, verify.
This series answers a top recurring question from finishing forums with platingclub line practice. Parameters are industry-standard starting ranges — confirm against your supplier TDS.
Triage: symptom → confirm → first move
| Symptom | Likely root | Confirm by | First move |
|---|---|---|---|
| Milky haze, wipes off | Rinse contamination / bath oil | White wipe cloth test | Skim + check rinse overflow |
| Gray haze, will not wipe | Low bath temperature or CrO3 drift | Thermometer + Ba titration | Hold 50–60 °C; correct ratio 100:1 |
| Haze in recesses only | Throwing power limit | Position map of parts | Aux anode or reduce load width |
| Iridescent yellow-blue | Catalyst ratio off ( sulfate ) | Hull cell panel | Adjust sulfate 0.8–1.2% of CrO3 |
| Haze after nickel, not on nickel | Nickel passivated before chrome | Timing check transfer | Cut transfer time; re-activate |
Engineer notes
- One variable per corrective action; verify by the confirm-by column.
- Records beat memory: log every trial on the tank card.
- Escalate when two consecutive actions fail — that is a senior call.
Safety: chromic acid mist is a carcinogen and burns skin. Mist suppressants, local exhaust and face shield are mandatory; report any chrome burn to first aid immediately.
FAQ
Haze in recesses but racks look fine — why?
Throwing power: high-CD faces plate, recesses go gray. Map positions and reduce load width or add aux anodes.
How does the sulfate ratio show up in a Hull cell?
Low sulfate = poor coverage band; high = bright narrow window. Both drift toward haze in production.
Why does nickel passivate before chrome?
Standing in rinse or acid kill; transfer over a minute lets the nickel surface oxidise. Chrome then plates hazy.