Scope of this guide
This senior guide covers the hard cases: combined variables, boundary conditions and the judgement calls that separate consistent lines from lucky ones.
Process: Pre-treatment & Cleaning. Figures in this guide are industry-standard starting ranges; confirm against your supplier TDS before locking settings.
Working ranges and control points
The table below is the daily reference for a cleaning line. Set by the card, verify by the control point column.
| Stage / parameter | Typical range | Control point | Watch out |
|---|---|---|---|
| Alkaline soak cleaner | 40–60 g/L, 55–70 °C | Titration 2× per shift | Oil layers shorten bath life |
| Soak time | 3–8 min | Visual water-break-free | Under-clean hides under wax |
| Rinse 1 (counter-flow) | TDS < 5000 ppm | Overflow checked hourly | Drag-in salts to next tank |
| Acid activate, 10–20% | 30–60 s | Bright, uniform etch | Over-etch on brass |
| Rinse after acid | Conductivity < 100 µS/cm | Before every plating tank | Chloride carry-over pits nickel |
Push The Boundary: the senior view
Beyond the basic card, this is the layer that matters at your level:
| Hard case | Why it is hard | Method | Data to keep |
|---|---|---|---|
| Mixed-alloy loads | Different windows collide | Split by family or map positions | Per-family thickness trend |
| Seasonal humidity swings | Flash and dry times move | Season-set viscosities | Monthly setting log |
| Recesses at spec limit | Throwing power ceiling | Auxiliary anode trials | Before/after thickness maps |
| Repeat claim from one customer | Use conditions differ | Reproduce their test | Claim-vs-lab correlation |
Standard routine
- Titrate cleaner bath at shift start
- Rack parts to avoid pockets that trap solution
- Observe water-break test after rinse
- Check acid bath strength before activation
- Record tank temps and concentrations in the log
Engineer notes
- Water-break-free surface is the pass criterion — droplets must sheet, not bead
- Counter-flow rinsing halves water use at the same cleanliness
- Replace cleaner before oil carry-over reaches the soak tank walls
- Acid activation time doubles for aged brass — adjust by visual etch
- Never let parts dry between stages; re-soak instead
Safety: Mixing acids and alkalis in the wrong order can splash hot solution. Add chemicals to water, never water to chemicals, and wear face protection.
FAQ
What is the fastest check that cleaning worked?
The water-break test: rinse and hold the part vertically; film should sheet without beads.
Why do parts flash-rust after rinse?
Rinse water is contaminated or dwell before plating is too long. Increase overflow and shorten transfer.
How often should cleaner baths be titrated?
At least twice per shift, plus after any heavy oil load.
How do I train juniors on this judgement?
Have them log the variable they changed and the measured result; review the log weekly against line outcomes.