Scope of this guide
Intermediate version: symptom-to-cause triage with the confirm-by column — find the variable, run one change, verify.
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
| Observation | Likely cause | Confirm by | First move |
|---|---|---|---|
| Rate drops late in bath life | Orthophosphite build-up | Turnover count + rate log | Plan rebuild at 5–6 turnovers |
| P content unknown, spec dispute | No assay routine | Lab assay per rebuild | Set assay schedule |
| Dark deposits, slow plate | pH low / stabilizer drift | pH + Hull cell | Hold pH 4.4–4.8 per TDS |
| Plate stops on recesses | Gas sticking, agitation dead | Position pattern | Work the agitation, not the bath |
| Bath decomposes (black rain) | Overload or palladium contamination | Load history | Strip load; discipline on make-up |
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: EN baths run hot and acidic with nickel salts and reducing agents. Heat gloves, face shield, ventilation; never add chemistry to a decomposing bath.
FAQ
Rate is half of yesterday — what first?
pH and temperature first, then loading state; orthophosphite builds late in bath life.
How do I count turnovers?
Metal added divided by bath metal content, summed; rebuild at the supplier's limit.
Why do recesses stop plating?
Hydrogen sticks there: agitation and rack motion, not more chemistry.