Surface treatment of turned parts — zinc plating, blackening, aluminium anodising and nickel plating — we arrange as part of the delivery. It is carried out by a vetted partner, but the order, the deadline and responsibility for the result stay with us. For you that means one order, one invoice and one person to call when something does not fit.
This article explains when a part really needs treatment, how the processes differ, and what therefore belongs in the drawing.
When a part needs treatment and when it does not
Material and the environment the part works in decide.
| Material | Environment | Recommendation |
|---|---|---|
| Free-cutting and structural steel | damp, outdoors, condensation | necessary — corrodes within weeks unprotected |
| Free-cutting and structural steel | dry indoor operation | consider — preservation oil is often enough |
| Stainless steel | ordinary conditions | usually not needed |
| Brass | ordinary conditions | usually not needed |
| Aluminium | abrasion, appearance, colour coding | consider anodising |
The second reason is often something other than corrosion: appearance, lower reflectivity, or a customer requirement for a uniform shade across an assembly.
The choice between “stainless without treatment” and “steel with plating” is also a cost decision — a comparison of both routes is in the article on how material affects price and time.
If you are unsure, write into the request what the part does and where it will work. Sometimes changing the material is cheaper than adding treatment — and sometimes the other way round.
The processes compared
Electroplated zinc
A layer of zinc is deposited electrolytically onto the surface. Zinc corrodes preferentially instead of the steel, so it protects the part even where the layer is damaged.
- Adds to the dimension roughly 5–15 µm per surface
- Protects reliably even in damp conditions
- On threads, expect the fit to tighten
Blackening
Chemical conversion of the surface into black iron oxide. Dimensions stay practically unchanged.
- No effect on dimensions — suitable for parts with tight tolerances
- On its own it gives little corrosion protection; it needs oil or wax
- Used mainly for appearance and lower reflectivity
Aluminium anodising
An oxide layer created electrochemically directly from the aluminium surface — unlike plating, nothing is deposited; the material itself is converted. The layer is hard, abrasion resistant and can be dyed.
- Grows into the material and out of it, roughly half each way
- Is electrically non-conductive — usually an obstacle on contact parts
- Applies only to aluminium; it is not used on steel or brass
Nickel plating
A nickel layer applied by electroplating. It is used where the appearance of zinc is not enough, or where the part has to withstand abrasion.
- Harder surface than zinc, suitable for moving parts
- Resists corrosion even in more demanding environments
- Adds to the dimension much like zinc — allow for it in tolerances
We do not offer hot-dip galvanising
Dipping into molten zinc is a technology for large steel structures — railings, posts, structural parts. The coating is thick and uneven and would ruin dimensions and threads on a precision turned part. Small turned parts use electroplated zinc only.
What belongs in the drawing
The most common source of misunderstanding is not the choice of process, but tolerance.
- Which surface is to be treated and which is not
- Whether the tolerance applies before or after treatment
- Required coating thickness, if it matters
- How the thread should behave — masked, or with the coating allowed for
- Any standard the treatment has to meet
Without stating whether the tolerance applies before or after treatment, you can end up with a part that is outside the drawing after plating — although it was correct after machining.
Why to leave it with the maker of the part
You can arrange treatment yourself. But that means a second supplier, a second order, transport there and back and — when something does not fit — two partners pointing at each other.
When the maker of the part arranges it:
- dimensions are correct after treatment too, because they knew about it while machining,
- responsibility sits in one place,
- transport between plants bypasses you,
- the quotation shows one price for a finished part, not two partial ones.
It does not raise the price — with us, surface treatment is one of the items making up the price of the part, alongside material, production, washing, inspection and transport.
What it does to the lead time
The part has to travel to the partner and back, so the lead time is longer than for an untreated part. That is why, on requests with surface treatment, we sometimes reply later than the usual 3–5 working days — we need the date confirmed by the treatment supplier so we do not promise something we cannot hold.
If the deadline is tight, say so in the request. Sometimes the part can be delivered in two waves: untreated pieces first for trials, the rest with treatment.
What Barluskat brings to this
We arrange zinc plating, blackening, aluminium anodising and nickel plating as part of the delivery. We produce precision turned parts Ø 3–35 mm on six sliding-head automatics by Tsugami and Star Micronics, from 1,000 pieces, in free-cutting steel, stainless steel, aluminium, brass and steel tube.
Besides surface treatment we also handle pressing and assembly — so you can receive the part ready to fit, or as a complete assembly. An overview is on the Manufacturing page.
Need a part including surface treatment? Send us the drawing and tell us what environment it will work in — we will propose the treatment and the material.