Scope of this guide
Senior version: the fix set with parameter windows, boundary cases and the discipline that keeps them fixed.
Series: finishing.com recurring questions answered 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 |
|---|---|---|---|
| Dull/gray only on edges & points | CD above bright range | Position map vs amps | Cut amps in steps; map again |
| Dull everywhere, worse at high CD | Brightener exhausted or overdosed | Hull cell panel | Hull cell before dosing |
| Dull after bath cools | Temperature below window | Temp log overlay | Hold 50–60 °C Watts band |
| Dull + rough together | Solids on top of CD stress | Filter ΔP + bag check | Filtration first, then amps |
| Dull band follows rack family | Old rack contacts hogging current | By-rack amp compare | Retire/rebuild those racks |
The fix set
- Fix 1 — CD window — Watts bright nickel typically 2–6 A/dm²; map positions and keep show faces inside band
- Fix 2 — temperature band — 50–60 °C ± 2 °C: cold bath dulls high-CD areas first
- Fix 3 — brightener by Hull cell — Dose from consumption curve; the panel reads bright range better than parts
- Fix 4 — pH hold — 3.8–4.4 in Watts: drift narrows the bright window before anything else shows
- Fix 5 — rack hygiene — High-mileage racks hog current; rebuild contacts on schedule
Case method
A line's dull edges moved with rack age, not bath chemistry: high-mileage contacts hogged current onto their parts. A rack rebuild schedule plus staged amp-in cleared the family. (Method illustration: compare dull rate by rack age on your own line.)
Engineer notes
- One variable per corrective action; verify with the confirm-by column.
- Records beat memory: log every trial on the tank card.
- Two failed actions in a row is a senior call — escalate with your log.
Safety: nickel salts are skin sensitisers; hot acid solutions splash. Face shield at tank, nitrile gloves, eyewash in reach.
FAQ
Map CD by position — how?
Thickness at five positions per rack, convert to CD, keep show faces inside 2–6 A/dm² band.
pH or brightener first when band narrows?
pH: it is free to correct and it narrows the window before brightener drifts.
Staged amp-in for dull parts?
Yes — full CD from zero seconds dulls thin edges; ramp helps them enter the window warm.