Capability

Surface Treatment & PVD

Corrosion, colour and friction — chosen as a system

Zinc & zinc-nickelNickelPassivationPVD in ten colours

PVD coated screws with a decorative pattern finish

Surface Treatment & PVD · Bekasi plant

Process overview

Corrosion, colour and friction — chosen as a system

A finish is not decoration applied at the end of the process — it changes the part. It changes the thread dimensions, the friction coefficient, the electrical behaviour of the joint and the way the screw behaves in a salt spray test. Choosing a finish is therefore a specification decision, not a purchasing one.

The range covers the conventional and the decorative. Electroplated zinc, zinc-nickel and nickel provide sacrificial corrosion protection and are the default for steel parts. Passivation restores the oxide layer on stainless steel after machining or handling. PVD deposits a hard ceramic film in vacuum, which is chosen for wear resistance, low friction and stable colour rather than for sacrificial protection — the two mechanisms should not be confused.

Step by step

How the process runs

Each step has a defined control point. The sequence is not arbitrary — changing it changes the result.

Pre-treatment

Parts are degreased and cleaned so that the coating or film bonds to the substrate rather than to contamination.

Plating or passivation

Zinc, zinc-nickel, nickel or passivation is applied, with thickness controlled against the specification.

Hydrogen relief

Hardened parts that have been electroplated are baked to remove hydrogen before it can cause brittle failure.

PVD deposition

For PVD, parts are loaded into a vacuum chamber where the film is deposited atom by atom onto the surface.

Thickness and colour verification

Coating thickness is measured, and PVD colour is compared against a retained master sample.

Re-gauging

Threads are gauged again after coating, because a finish that adds thickness can move a thread out of its fit class.

Specification

Process window and capability

The numbers below define what the process can hold repeatably. They are not laboratory bests.

Plated finishes

Zinc (blue-white, colour, black, green), zinc-nickel alloy, nickel

Conversion finishes

Passivation for stainless steel

Coated finishes

Nano coating, stoving paint (colour matched)

PVD film

Vacuum deposited ceramic film, nano to micrometre thickness

PVD colours

Silver (2), black (2), gold (2), rose gold, dark brown (2), blue

Effect on thread

Plating adds thickness; PVD is thin enough not to affect the fit

Hydrogen risk

Present with electroplating, absent with PVD

Selection drivers

Corrosion, appearance, friction, electrical contact, dimensional effect

Equipment

What the line is built on

Capacity figures are per machine and assume a standard part. Complex geometry reduces throughput.

Equipment	Specification
Plating lines	Zinc, zinc-nickel and nickel electroplating
Passivation line	Stainless steel passivation after machining and handling
PVD chambers	Vacuum deposition for decorative and wear-resistant films
Film thickness gauge	Coating thickness measurement
Salt spray chamber	Neutral salt spray corrosion testing

Process control

What is checked, and when

A control that is not recorded is not a control. Each item below generates a record linked to the lot code, retained for the programme duration.

Quality & certifications

Coating thickness measured per batch

Salt spray testing where a corrosion grade is specified

Appearance inspection against a retained master sample

Thread gauge after coating

Hydrogen relief record for hardened plated parts

Adhesion and colour check on PVD batches

Questions

Surface Treatment FAQ

Practical questions from sourcing and engineering teams.

Considering a process change? If a tolerance or finish is not achievable on our current line, we will say so before quoting rather than after the first lot.

Zinc or zinc-nickel?

Zinc is the general-purpose sacrificial coating. Zinc-nickel is chosen where more corrosion resistance is needed from the same film thickness, which matters on a small part where a thick coating would close the thread.

Why choose PVD instead of plating?

For wear, colour stability and dimensional control. A PVD film is hard, does not peel or fade like a plated colour, and is thin enough that it does not change the thread fit. It is not a sacrificial corrosion coating, so it is not the right answer if the requirement is salt spray hours.

Can a coating make a thread fail its gauge?

Yes. Plating adds thickness to the flank, so a thread that gauges correctly before coating can fail after it. That is why threads are re-gauged after coating, and why plating thickness is a specification rather than a process detail.

Does passivation add a layer?

No — it restores the passive oxide layer on stainless steel rather than depositing a coating. It is applied after machining or handling that has disturbed the surface, and it does not change the dimensions.

Related capabilities

What happens before and after

These processes are usually sequenced with the one above.

Heat treated black oxide socket head screws

Capability

Heat Treatment

Hardening, tempering and case hardening set the balance between a wear-resistant surface and a core that will not fracture — with hydrogen relief where plating demands it.

Capability

Surface Treatment & PVD

Zinc, zinc-nickel, nickel, passivation and PVD finishing, selected for corrosion resistance, appearance, electrical behaviour and the effect on thread fit.

Plated socket head screws inspected in the laboratory

Capability

Inspection Laboratory

Metallography, hardness, dimensional measurement, tensile, friction, salt spray, coating thickness and RoHS testing, all in-house so a question can be answered without waiting for an outside lab.

Need surface treatment for your part?

Send the drawing and the annual volume. We will confirm feasibility, tolerance and lead time in the quotation.

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