Surface treatment
What we run in-house, and what we specify
In-house
- CoatingBlack oxide
- CoatingAnodizing — Type II / Type III
- MarkingLaser marking
Through qualified partners
- PlatingZinc — clear, blue, yellow, black chromate, zinc-nickel (ASTM B633 / ISO 4042)
- PlatingElectroless nickel
- PlatingThin dense chrome
- CoatingPVD, powder coating, passivation
- HeatHeat treatment and hardening
Black zinc is not standard zinc plating. If your print calls for a black finish, it needs black chromate specified — we will confirm it with you before the part is plated, not after.
Heat treatment
The conditions we specify and check
| Process | What it does | Grades we run it on | Typical result |
|---|---|---|---|
| Stress relief | Takes out the stress left by welding and heavy roughing so the part does not move on the finishing cuts. | SS400 · S355JR welded frames · 6061 plate | No hardness change — dimensional stability |
| Annealing | Softens the steel so it can be cut. The hardening comes afterwards, not before. | SUJ2 · SKD11 · SKD61 before machining | Machinable condition, SUJ2 typically under 210 HB |
| Normalizing | Refines and evens out the grain after hot working so machining behaves predictably. | S20C · S45C · SS400 | Uniform structure through the section |
| Through hardening — quench and temper | Hardens the full section, then tempers back to the toughness the part needs. US drawings often write this simply as HT. | SCM440 / 4140 · SNCM439 / 4340 · S45C · S50C | 4140 HT commonly 28–34 HRC; higher on request |
| Case hardening — carburizing | Puts a hard wearing skin over a core that stays tough. Case depth is a drawing item, not a default. | S20C / 1020 bushings, pins, wear plates | Case typically 58–62 HRC over a soft core |
| Induction hardening | Hardens only the running surface of a shaft and leaves the rest of the part alone. | S45C / 1045 shafts and pins | Typically 45–55 HRC on the hardened band |
| Tool steel hardening | Harden and temper several times for dies, punches and hot-work tooling. | SKD11 / D2 · SKD61 / H13 | SKD11 typically 58–62 HRC · SKD61 typically 44–52 HRC |
| Precipitation hardening — aging | On PH stainless the aging condition is part of the specification, not an option. H900 and H1075 are different materials in practice. | SUS630 / 17-4PH · 15-5PH | H900 about 40–44 HRC · H1075 about 32–36 HRC |
| Solution treat and artificial aging | The T temper on aluminium is a heat treatment. T6 and T651 are not the same stock condition — T651 is stress-relieved plate. | 6061-T6 / T651 · 7075-T6 · 6063-T5 / T6 | Supplied in temper; we do not re-heat-treat aluminium in process |
Where it is done. Heat treatment runs through qualified partners under our inspection, not in our own furnaces. We hold the specification, and every hardened batch is checked on our Mitutoyo QMH 14BX before it ships.
The hardness figures above are typical ranges for these grades, not a specification. Your drawing governs — send it with the condition, hardness and case depth called out and we will quote against those, not against the table.