aseanzip_boss · 2 hours agoPitting is the most-asked bright nickel defect on finishing forums — and the most common first answer, “add anti-pitting additive”, is wrong more often than right.
There is no generic pitting: there are six pit types, six causes, six fixes. Here is the 10-minute magnifier routine we run on our own lines.
The 10-minute triage table
| Pit type (magnifier) | Signature look | Root cause | First fix |
|---|---|---|---|
| Gas pit | Teardrop tail, shiny bottom | Hydrogen sticking to the part | Surface tension 35–45 dyn/cm |
| Solids pit | Gritty rough bottom | Particles in bath or on part | Filter 2–5 turns/h at 5 µm |
| Burn pit | Dendritic, on high-CD zones | Local current density too high | Lower CD / reposition anodes |
| Base-metal pit | Substrate visible in pit | Porosity or scale on casting | Bake-test; fix casting first |
| Oil pit | Doughnut ring, wet look | Oil droplet pinned to surface | Skim, degrease, find the leak |
| Organic pit | Irregular, random spread | Decomposed brightener | Hull cell test; carbon treat |
The 10-minute routine
- Photograph the part before touching it — the pit pattern is evidence
- Magnifier pass: classify each pit (tail = gas, grit = solids, ring = oil)
- Position test: mark the rack row of every pit cluster
- Swap test: move the suspect rack position to the middle for the next load
- Run one corrective action only; Hull cell before and after
- Log dose, readings and outcome on the tank card
Engineer notes
- Most pitting calls are gas pits misdiagnosed — measure surface tension before adding anything
- Bottom-row pitting with a clean bath means agitation dead zone, not chemistry
- Boric acid below 40 g/L burns before it pits; keep 40–50 g/L in Watts
- Pits that show substrate metal are not a plating problem — fix casting first
Safety: hydrogen from bright nickel baths is explosive at 4–75% volume in air — keep lids open, ventilate, no flames. Nickel salts are skin sensitisers.
Full version with Fixes A–F (parameter windows), FAQ and the 8%→0.5% case study:
Bright Nickel Pitting: How to Tell Gas Pits From Every Other Kind in 10 Minutes — platingclub.com
Questions welcome below — post your pit photos with rack position and we will help you triage.