Core Mechanism Boosting Nickel Ductility
Sodium Allyl Sulfonate (SAS/ALS, 35% liquid plating grade) acts as stress relieving auxiliary brightener in acid nickel baths:
- Its sulfonate group evenly adsorbs on cathode surface, slowing fast nickel crystal vertical growth, prompting fine, compact equiaxed crystal formation.
- Refines grain size to eliminate columnar brittle crystals that easily crack under bending or stamping.
- Neutralizes excessive tensile stress induced by high-concentration secondary brighteners like butynediol, lowering internal coating tension significantly.
- Reduces microcavities and pinholes inside nickel deposits to avoid fracture origins under mechanical deformation.
Performance Benefits
- Coating resists cracking during post-plate bending, crimping, deep drawing and assembly forming
- Less peeling or flaking when substrates undergo impact and thermal cycling
- Balances brightness and flexibility, ideal for decorative hardware, auto parts and electronic connectors requiring post-processing
- Extends service life of nickel layers under repeated deformation load
Optimal Working Dosage for Ductility
Target pure SAS concentration in bath: 0.7–1.4 g/L
Corresponding 35% SAS liquid addition: 2–4 mL/L plating solution
- Below 0.5 g/L pure SAS: High internal stress, brittle nickel easy to crack
- Over 2 g/L pure SAS: Excess organics cause hazy, yellow coating with slightly raised stress
Matching Bath & Operation Tips
- Maintain bath temperature 50–60℃, pH 4.0–4.8 with moderate air agitation for uniform additive adsorption
- Combine with low-stress secondary brighteners; avoid over-dosing alkynol brighteners
- Regular activated carbon filtration every 2–3 weeks to remove degraded SAS organic residues
- Dummy plating periodically to eliminate harmful decomposition byproducts that damage ductility
Grade Selection
35% low-impurity aqueous SAS liquid is the best choice for plating lines: dust-free, direct dosing, uniform distribution across the bath to stabilize coating flexibility batch by batch.
