? Where is your part right now?

Not made yetWe machine it and galvanize it in one order — no separate shipping, no re-inspection between shops.Machine + finish from one order →Already madeSend us your finished parts. We check them against the fit rules below, then coat and return.Check if your part qualifies →Still comparing processesFour galvanizing routes differ by an order of magnitude in coating thickness. Start with the comparison.Compare the four routes →

SURFACE FINISHING

Galvanizing Service

Hot-dip galvanizing Zinc electroplating Sherardizing Zinc thermal spray

A sacrificial zinc layer that corrodes before the steel does. Four routes sit under one name, and they differ by more than an order of magnitude in coating thickness — which is the number that decides whether your threads still fit afterwards.

Get a quote Check if my part qualifies

5 – 300 µmZinc coating thickness across the four routes

Every coated surface growsThickness adds to bores and threads on both sides

ASTM D6386, D7803Hot-dip thickness measured to standard

Lead time & max part sizeTo confirm with the shop

Galvanized steel parts with a bright spangled zinc coating after hot-dip galvanizing — Hot-dip galvanized steel parts — the spangle pattern is normal and does not affect corrosion performance.

Sequence

Galvanizing is the last step — everything before it changes the result

A coating cannot fix what happened upstream. Weld, braze and stress-relieve first; coat last. Here is where this operation sits and what it depends on.

STEP 1MachineMill, turn or fabricate to drawing

STEP 2DeburrBurrs and sharp edges are coated, not removed, by zinc

STEP 3Weld / stress relieveMust happen before coating — heat destroys zinc at the joint

STEP 4GalvanizeYou are here — 5–300 µm of zinc, route dependent

STEP 5InspectCoating thickness and appearance

Two things follow from this order. First: if the part is already welded, we need to know, because the weld zone is where a coating is thinnest. Second: if a machined feature has to stay uncoated, that has to be marked before the part reaches the bath — see drawing notes.

Hot-dip galvanizing process flow diagram: degreasing, rinsing, pickling, rinsing, flux solution, drying, zinc bath, then cooling and inspection

The hot-dip sequence in full — five of the eight stages are surface preparation, before the part ever reaches the zinc.

Overhead crane lifting a jig of steel fabrications out of the molten zinc bath on a galvanizing line — A jig of steel fabrications being lifted from the molten zinc bath.

Freshly galvanized steel parts hanging bright silver on a jig straight out of the zinc bath — Straight out of the bath — the bright finish is the zinc layer itself, not a paint.

Fit check

Can we galvanize your part? Three things decide it

Base material, part size and geometry. Run through these three before you send a drawing — it takes a minute and saves a round trip.

Base material

Yes — steel, alloy steel, cast iron
No — aluminium, copper, brass, titanium
No — plastics, composites

Galvanizing bonds zinc to iron. For non-ferrous parts, see alternative processes.

Part size & weight

Hot-dip requires the part to be fully immersed in a zinc bath
Thermal spray has no bath limit — it is the route for oversized parts
Max envelope and weight per route: To confirm

Tell us the largest dimension and the weight and we will confirm the route.

Geometry

Sealed cavities trap air in the bath — vent and drain holes are required
Very fine threads and blind holes fill with zinc
Distortion risk on thin, long or asymmetric sections needs review

Tubular and box assemblies: drill a vent hole before coating, not after.

Specifications

Hot-dip galvanizing: 85 – 200 µm zinc coating, measured to ASTM D6386

The numbers a buyer asks for before sending a drawing.

Process

Four routesHot-dip · electroplating · sherardizing · zinc thermal spray

Coating thickness

5 – 300 µm85–200 hot-dip · 5–25 electroplated · 10–30 sherardized · 100–300 sprayed

Spec standard

ASTM D6386, D7803Thickness measured on hot-dip coatings

Base materials

Ferrous onlySteel and iron · alloy steels · cast iron

Max part size · lead time

To confirmBath envelope, weight limit and schedule

Price band

To confirmQuoted per part, by size, weight and quantity

Still open: achievable surface roughness, salt-spray hours, maximum part size, lead time and price band are not published yet. They will be added as figures once the shop confirms them — not as adjectives.

Dimensional change

What each route adds to your part — and when that breaks the fit

A coating is material that was not there when you machined the part. It goes on every wetted surface, inside holes and on threads as well as outside.

Route	Coating per surface	Effect on a mating dimension	What to do
Zinc electroplating	5 – 25 µm	Tightest route. On a 20 mm shaft this is up to 0.05 mm on diameter.	Normally usable on precision parts without masking.
Thermal diffusion (sherardizing)	10 – 30 µm	Thin and uniform — the most even coverage of the four.	Suits parts with fine features.
Hot-dip galvanizing	85 – 200 µm	On a 20 mm shaft this is up to 0.40 mm on diameter across both sides.	Mask or re-tap any thread or bore that has to assemble.
Zinc thermal spray	100 – 300 µm	Thickest route — build-up is the point of it.	For oversized structures; keep it away from fits.

Coating thickness per surface, as published for each route. Both sides of a dimension grow: a shaft measured across grows by twice the figure shown.

Have a critical fit on the drawing? Mark the surface and we will mask it before coating — or quote a thinner route that clears the tolerance.

Get a quote

Four routes

Which galvanizing route fits your part

All four deposit zinc. They differ by thickness, by how evenly they coat a thread, and by whether your part has to fit in a bath.

Large steel fabrications on a jig being lifted from the hot-dip zinc bath

Hot-dip galvanizing

85 – 200 µmASTM D6386, D7803

Immersion in molten zinc for comprehensive coating. Excellent durability and decades of longevity; ideal for large, complex structures.

Finish options: passivation, chromate conversion

Not for: tight-tolerance threads or bores, thin sections prone to distortion, or parts that cannot be fully immersed.

Bright zinc electroplated steel brackets with a smooth, uniform finish

Zinc electroplating

5 – 25 µm

Precision zinc coating applied through electrical deposition. High precision and uniformity; ideal for small, intricate components.

Finish options: bright finish, chromate conversion, passivation

Not for: large structures, or parts needing thick sacrificial build-up.

Sherardized hex bolts with a thin, matt grey zinc alloy coating

Thermal diffusion galvanizing (Sherardizing)

10 – 30 µm

Zinc alloy coating applied through a diffusion process. A very thin, uniform coating with high adhesion and corrosion resistance.

Finish options: bright finish, passivation

Not for: parts needing maximum coating thickness in one pass.

Operator guiding a galvanized steel plate out of the zinc bath with a hooked pole

Zinc thermal spray

100 – 300 µm

Zinc coating applied through a thermal spray process. High build-up capability; suitable for large or irregularly shaped components.

Finish options: passivation, topcoats

Not for: small precise parts, deep bores, or surfaces out of line of sight.

Capability	Description	Specifications	Finishing options	Unique features
Hot dip galvanizing	Immersion in molten zinc for comprehensive coating.	85-200 μm,(ASTM D6386, D7803)	Passivation, chromate conversion	Excellent durability and decades of longevity; ideal for large, complex structures.
Electroplating	Precision zinc coating is applied through electrical deposition.	5-25 μm	Bright finish, chromate conversion, passivation	High precision and uniformity; ideal for small, intricate components.
Thermal diffusion galvanizing (Sherardizing)	Zinc alloy coating is applied through a diffusion process.	10-30 μm	Bright finish, passivation	Offers a very thin, uniform coating with high adhesion and corrosion resistance.
Zinc thermal spray	Zinc coating is applied through a thermal spray process.	100-300 μm	Passivation, topcoats	High build-up capability; suitable for large or irregularly shaped components.

Coating thickness and finishing options as published for each route.

Pick or avoid

When galvanizing is the right call — and when it is not

Pick galvanizing when

The part lives outdoors and corrosion is the failure mode you are designing against.
The base material is steel, alloy steel or cast iron.
You want sacrificial protection — the zinc corrodes first, even at a scratch or cut edge.
Coating thickness variation is acceptable on non-mating surfaces.

Avoid galvanizing when

You hold a tight tolerance on a mating face — see dimensional change.
You need a specified RAL colour; use powder coating.
The part is aluminium, copper or plastic — see materials.
The part will be welded after coating.
You need a mirror finish; see polishing.

Still between galvanizing and powder coating? Both quote the same day — send one drawing and ask for both.

Get a quote

Drawing notes

What to write on the drawing so we coat it the way you meant

Most coating problems start with an unclear note, not an unclear process. Copy these into your drawing and edit the numbers to match your own spec.

1.  HOT-DIP GALVANIZE ALL SURFACES.    COATING THICKNESS 85-200 um, MEASURED TO ASTM D6386 / D7803.2.  MASK ALL TAPPED HOLES AND MATING FACES BEFORE COATING.    SEE VIEW A FOR MASKED AREAS.3.  PROVIDE VENT AND DRAIN HOLES - MIN 6 mm - FOR THE MOLTEN ZINC BATH.    DO NOT SEAL CAVITIES BEFORE COATING.4.  UNLESS NOTED OTHERWISE, APPEARANCE PER SUPPLIER STANDARD.    SPANGLE PATTERN AND SLIGHT COLOUR VARIATION ACCEPTABLE.5.  DO NOT RE-MACHINE COATED SURFACES.

Examples only — replace the standard callout and thickness with your own requirement. Tell us which surfaces are masked and we will confirm them before the coating runs.

Materials

Which base materials we can and cannot galvanize

Galvanizing is a ferrous process — the zinc has to bond to iron. If your material is not on the left column, the right column tells you what to use instead.

Base material	Galvanizing	Notes	Use instead
Steel and iron	Yes	Most predictable coating thickness and appearance.	—
Alloy steels	Yes	Silicon and phosphorus content drives coating thickness — tell us the grade.	—
Cast iron	Yes	Abrasive cleaning required to remove the casting skin; coating runs thicker.	—
Stainless steel	Not normally	Zinc on stainless adds a dissimilar-metal couple without adding useful protection.	Passivation · Plating
Aluminium	No	Zinc does not bond usefully to aluminium.	Anodizing · Powder coating
Copper and brass	No	Galvanizing a copper alloy creates a couple that attacks the zinc.	Polishing · Plating
Plastics	No	No metallic surface for zinc to bond to.	Painting

Parts in more than one material? Send the assembly and we will route each component to the process that fits it.

Get a quote

Applications

Where galvanized parts end up

Every application below is one where the part is expected to survive weather for years without maintenance.

Galvanized steel farm fencing in an outdoor agricultural setting

Agriculture and farming

Fencing, gates, troughs and equipment frames exposed to weather and livestock.

Galvanized structural steel sections stacked on a construction site

Construction and infrastructure

Structural steel, fixings, walkways, guardrails and bridge hardware.

Automotive

Chassis brackets, fasteners and underbody hardware exposed to road salt.

Galvanized steel pipe used for energy and fluid transport

Energy and transport

Pipework, supports and transmission hardware in outdoor service.

Galvanized steel ducting and ventilation system components

Ventilation systems

Ducting, housings and fixings in humid or corrosive air streams.

Solar panel mounting structure made from galvanized steel

Solar mounting

Frames, clamps and ground mounts with a 20-plus year outdoor design life.

QA and documentation

What you get back with the parts

Purchasing usually needs paper as well as parts. Here is what we can issue today and what is still being confirmed.

Available

Coating thickness

Measured to ASTM D6386 and D7803 on hot-dip coatings.

To confirm

Material certificate

Mill certificate for the base material — subject to the material arriving with one.

To confirm

Salt-spray report

Hours to first red rust, per route. Being confirmed with the shop.

To confirm

RoHS / REACH

Compliance statement for the coating chemistry.

Galvanizing guides and comparisons

Longer answers on the questions this page only has room to state.

What is galvanized metal?

How the coating forms, what spangle means, and how galvanized steel compares with uncoated steel.

Galvanneal vs galvanized steel

The difference between the two coated sheet products, and when each is worth specifying.

Zinc plating colours

What clear, blue, yellow and black chromate actually change — appearance and corrosion resistance.

Zinc plating service

The electroplated route in detail, for small parts that need a controlled thin coating.

Powder coating service

When a coloured organic layer beats a sacrificial zinc layer — and when it does not.

All surface finishing options

Compare all 20 finishes by roughness, thickness, corrosion and cost.

FAQ

Galvanizing FAQ: the questions engineers ask us

Can you galvanize stainless steel or aluminium?

No. Galvanizing bonds zinc to iron, so it is a ferrous process. Stainless steel is normally passivated, aluminium is anodized, and copper alloys are polished or plated. If you searched for anodized steel, what you probably want is passivation — anodizing is an aluminium process.

How thick is a hot-dip galvanized coating?

85–200 µm, measured to ASTM D6386 and D7803. The exact figure depends on steel thickness and silicon content, not on how long the part stays in the bath.

Will galvanizing change my part dimensions?

Yes. The coating adds thickness to every wetted surface, including bores and threads. A shaft measured across grows by twice the per-surface figure. See the dimensional change table, and mark any critical surface for masking.

Which route suits small precision parts?

Zinc electroplating at 5–25 µm. It deposits far more evenly than hot-dip, which is why it is the standard choice for small intricate components.

Can galvanized parts be welded?

Weld before coating. Welding after galvanizing burns off the zinc at the joint and the fumes are hazardous. A post-weld repair has to be re-coated locally with zinc-rich paint.

Do I need vent and drain holes?

For hot-dip, yes — sealed cavities trap air and prevent the zinc from reaching the inside of a hollow section. They also let the part drain as it leaves the bath. Mark them on the drawing; see the drawing notes.

Do you coat customer-supplied parts?

Yes. Run the three checks under fit check first — base material, part size and geometry. Size and weight limits per route are being confirmed with the shop.

What colours are available?

Galvanizing is not a colour process. The finish options are passivation, chromate conversion, bright finish and topcoats — all variations on the zinc itself. For a specified RAL colour, use powder coating.

Get your galvanizing quote

Upload a STEP, IGES or PDF drawing. Tell us the base material, the quantity, and which surfaces must stay uncoated — we will come back with the route, the coating thickness and the lead time.

Get a quote Machine it first

What to send us

Drawing — 2D and 3D files (STEP, IGES or PDF).
Quantity — number of units, including any spares.
Base material — the grade, or describe the application.
Required finish — which route, and the coating thickness if you have a spec.
Masking — which surfaces must stay uncoated, and any thread or bore that has to assemble.
Anything else — welding, prior heat treatment, or a surface that is already damaged.

All uploads are secure and confidential. Engineers review and reply with a quotation and lead time.