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Not made yetWe machine the aluminium part and alodine it in one order — the coating does not fill machining marks, so the surface we leave matters.Machine + coat from one order →Already madeSend us your aluminium parts. Alodine is an immersion process — the part has to fit in the bath and be reachable by the solution.Check if your part qualifies →Still comparing processesAlodine and anodizing are both for aluminium but do different jobs. The comparison below is the fastest way to pick.Alodine or anodizing? →

SURFACE FINISHING

Alodine Coating Service

Clear Gold Aluminium only Immersion process

A chromate conversion coating — also called chem film — formed by immersing aluminium in a solution of chromium ions. The layer is thin, protective, and it is the low-cost route for aluminium parts that need corrosion protection without a heavy coating.

Get a quote Check if my part qualifies

Aluminium onlyThe substrate has to be aluminium or an aluminium alloy

Clear or goldTwo published colours

ImmersionThe part is dipped — the solution has to reach the surface

Layer thicknessTo confirm with the shop

Aluminium pins with a gold chromate conversion coating after alodine treatment — The gold colour is the chromate conversion layer itself — a thin film formed on the aluminium, not a paint or a plate.

Sequence

Alodine is an immersion step — cleaning before it decides whether it takes

This is a conversion coating: the solution reacts with the aluminium surface itself. Anything on that surface — oil, oxide, a fingerprint — stops the reaction locally, so the part comes out patchy.

STEP 1MachineMill, turn or fabricate the aluminium part

STEP 2Deburr & cleanContamination blocks the conversion reaction where it sits

STEP 3Any anodizing or weldingDecide the order — see the note below

STEP 4Alodine dipYou are here — clear or gold conversion layer

STEP 5InspectColour uniformity and coverage in recesses

Order matters if the part is also being anodized or welded. Alodine is a conversion coating, so a later anodizing step would replace it rather than sit on top. Tell us the full process route when you order — see design constraints.

A chemical conversion coating line with treatment tanks and a rinse station — The dip line: the part travels through the solution rather than being sprayed.

Close view of a gold chromate conversion coating on a machined aluminium part — Up close, the conversion layer follows every machined face.

Fit check

Can we alodine your part? Three things decide it

Substrate, size and the process route around it. Run through these three before sending a drawing.

Substrate

Yes — aluminium and its alloys
No — steel, stainless steel, copper, brass, titanium
Not on the published list: ask first

For non-aluminium parts, the equivalent protective step is different — see materials.

Size & geometry

Immersion process — the part has to fit the treatment tank
The solution must reach the surface, so blind cavities are a risk
Maximum part envelope: To confirm

Tell us the largest dimension and whether the part has closed or deep internal features.

Process route

Alodine is a conversion coating — it becomes part of the surface
A later anodizing step would replace it, not layer on it
Welding after coating damages the layer at the joint

Give us the full route — machining, welding, anodizing, alodine — so the order can be set correctly.

Specifications

Alodine: 2 colours, clear or gold, on aluminium — applied by immersion

Every value below is taken from our published specification for this process.

Materials

AluminiumThe conversion reaction is specific to aluminium and its alloys.

Colour

Clear or goldBoth are published options for this process.

Process

ImmersionParts are dipped into a chromium-ion solution — a rapid, low-cost route.

Texture

Follows the substrateThe layer is thin and conforms — it does not fill machining marks.

Layer thickness

To confirmNot published for this process yet — being confirmed with the shop.

Available colours

Clear · goldAsk for the colour you need when you order.

Read this before specifying: alodine is described in our own documentation as a low-cost surface finishing approach for aluminium and its alloys. If the part needs a hard, wear-resistant oxide layer rather than a thin conversion film, anodizing is the process you want.

What it adds

A conversion layer is thin — the dimensions barely move

Alodine converts the top of the aluminium surface rather than depositing metal on it. The layer is a fraction of what a plating or a paint would add.

Where it acts	Effect	Why it matters	What to do
Toleranced faces	Negligible build-up	Unlike plating, a conversion coating does not close up a bore or grow a shaft meaningfully.	Normally no masking needed for tolerance reasons.
Electrical contact points	Layer is conductive at the contact	This is why alodine is specified on electrical hardware — it protects without insulating.	Confirm with your electrical requirement.
Threads	Minimal fill	Threads stay usable where a plated layer would have to be masked.	Flag fine threads if the fit is critical.
Appearance	Colour is part of the surface	A scratch through the layer is visible as bare aluminium.	Say if the visible face has to be free of marks.

Published layer thickness for alodine is not yet available; the behaviour above follows from the process being a conversion coating rather than a deposit. The figure will be added once the shop confirms it.

Need the layer thickness quantified before you commit? Ask us and we will confirm it against your drawing.

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Clear or gold

Clear or gold: alodine against anodizing, and against itself

Alodine comes in two published colours. But the bigger decision is usually alodine versus anodizing — both are aluminium processes and they are not interchangeable.

Machined aluminium parts on a bench after chromate conversion coating

Alodine — clear

Clear film

The clear version leaves the aluminium looking close to its natural colour while still protecting it. The layer is thin and follows the machined surface.

Best for: parts where you want protection without changing the appearance much

Not for: parts that need a hard wear-resistant surface — a conversion film is not a thick oxide layer.

Alodine — gold

Gold film

The gold appearance is characteristic of the chromate conversion layer and is the version most often seen on hardware and electrical parts.

Best for: hardware, tools and electrical components where the colour signals the treatment

Not for: colour-matching to a painted assembly — this is a coating colour, not a paint colour.

Alodine or anodizing for your aluminium part? Send the drawing and describe what the surface has to do — protect, wear, or conduct.

Get a quote

Pick or avoid

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

Pick alodine when

The part is aluminium or an aluminium alloy — this is a requirement, not a preference.
You want corrosion protection at a low cost per part.
The part is a tool, a piece of hardware or part of an electrical system — the three applications named in our published specification.
You need protection without a thick layer that would change fits.
The part is dipped — so it has to be reachable by the solution.

Avoid alodine when

The material is not aluminium — steel, copper and titanium all need a different process. See materials.
You need a hard, wear-resistant surface — anodizing builds an oxide layer, alodine converts the surface in place.
The part is welded after coating — the joint has to be treated again.
You need a specified paint-like colour — the two published colours are clear and gold.

Aluminium part needing more than a thin film? Ask for anodizing and alodine side by side on the same drawing.

Get a quote

Design constraints

What decides whether the alodine layer comes out even

Three variables: how clean the surface arrives, whether the solution can reach it, and where alodine sits in the process route.

Surface cleanliness

The conversion reaction happens on the aluminium itself. Oil, oxide, coolant residue or a fingerprint blocks it exactly where it sits, and the part comes out patchy.

Solution access

Immersion means the solution has to reach the surface. Closed cavities and deep blind features trap air and stay untreated — call them out on the drawing.

Route order

A conversion coating is part of the surface, so a later anodizing step would replace it. Set the order before the parts are made, not after.

Handling after coating

The layer is thin compared to a plating. Handling marks and scratches show as bare aluminium, so parts should be packed rather than loose-bagged.

Masking

Because the build-up is negligible, masking is usually unnecessary for tolerance reasons — it is only needed if a surface must stay uncoated for a functional reason.

Colour expectation

Clear and gold are the two published options. On a machined surface the colour follows the surface finish, so a directional machining pattern stays visible through the film.

Drawing notes

What to write on the drawing so the conversion layer comes out even

For alodine the note is mostly about cleanliness, access and order — masking rarely matters because the layer barely adds thickness.

1.  ALODINE (CHROMATE CONVERSION COAT) ALL SURFACES.    COLOUR: CLEAR / GOLD  (delete one)2.  CLEAN AND DEGREASE BEFORE COATING.    NO OIL, COOLANT RESIDUE OR OXIDE ON COATED SURFACES.3.  PROVIDE ACCESS FOR THE SOLUTION:    NO SEALED CAVITIES. VENT BLIND FEATURES.4.  PROCESS ORDER: MACHINE - DEBURR - ALODINE.    DO NOT ANODIZE OR WELD AFTER ALODINE.5.  HANDLE COATED PARTS WITH GLOVES.    PACK SO COATED FACES DO NOT RUB.

Examples only. The line that most often goes missing is the process order — alodine sits last among the chemical steps, not before them.

Materials

Which materials take alodine — and what to use if yours does not

The conversion reaction is specific to aluminium. Every other substrate needs a different process, and the table below names which one.

Material	Alodine	Notes	Use instead
Aluminium and its alloys	Yes	The substrate this process is for. Clear or gold, applied by immersion.	—
Steel and stainless steel	No	The reaction does not apply to ferrous surfaces.	Black oxide · Passivation
Copper and brass	No	Copper alloys need their own protective treatments.	Electroplating · Polishing
Titanium	No	Titanium is anodized rather than chromate converted.	Anodizing
You need a hard wear layer	Use anodizing	Anodizing builds an oxide layer; alodine converts the surface in place.	Anodizing
You need colour beyond clear/gold	Use anodizing	Anodizing offers clear, black, grey, red, blue and gold on aluminium.	Anodizing

Part 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 alodine is used

Our published specification names three application areas for alodine. They share one trait: the part needs protection without gaining a thick, insulating layer.

Gold chromate conversion coating on a machined aluminium part

Tools

Hand tools and fixtures where a protected surface is handled constantly and a thick coating would change the feel and the fit.

A production tray of small aluminium parts with a gold chromate conversion coating

Hardware

Fasteners and fittings that need corrosion protection in service, at low cost per part.

Gold chromate coated aluminium pins of the kind used in electrical connectors

Electrical systems

Enclosures, busbar and connector hardware — where the coating protects the aluminium without behaving like an insulator.

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

Colour and coverage

Visual check for uniform colour and full coverage on specified faces.

Available

Process route

Coating confirmed as the last chemical step in the route.

To confirm

Layer thickness

Measured conversion layer thickness. Being confirmed with the shop.

To confirm

Corrosion testing

Salt-spray hours for the coated surface. Being confirmed with the shop.

Alodine and chromate conversion guides

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

Alodine coating: what it is, benefits and how it works

The process behind the colour, and where it sits against anodizing.

Alodine aluminum coating

Aluminium-specific notes on the conversion reaction and its limits.

Alodine vs anodize

The comparison most buyers arrive with — protection versus hardness.

Anodizing service

When the part needs a built-up oxide layer instead of a conversion film.

Passivation service

The equivalent protective step for stainless steel parts.

All surface finishing options

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

FAQ

Alodine FAQ: the questions engineers ask us

What is alodine?

Alodine — also called chem film or chromate conversion coating — is a thin protective layer formed on the surface of a substrate by a solution containing chromium ions. The layer protects against corrosion and gives the part a distinct appearance.

Is alodine the same as anodizing?

No, and the difference matters. Anodizing builds up an oxide layer on aluminium and gives a hard, wear-resistant surface. Alodine converts the top of the surface in place and stays thin. Pick anodizing for wear and colour; pick alodine for low-cost protection that keeps the fits.

Which materials can be alodined?

Aluminium and its alloys — that is the substrate our published specification covers. Steel is black-oxided or passivated instead, copper alloys are plated or polished, and titanium is anodized.

Which colours are available?

Two: clear and gold. The gold colour is characteristic of the chromate conversion layer itself, not a dye or a paint.

Will alodine change my part dimensions?

Barely. It is a conversion coating rather than a deposit, so it does not close up bores or grow shafts the way plating does. That is why masking is normally not needed for tolerance reasons. The exact layer thickness is being confirmed.

Why did my part come out patchy?

Almost always contamination. The solution reacts with the aluminium surface itself, so oil, oxide or coolant residue blocks the reaction exactly where it sits. Cleanliness before the dip is the deciding factor.

Can I anodize after alodining?

Do not plan it that way. Alodine becomes part of the surface, so a later anodizing step replaces it rather than sitting on top. Give us the full process route when you order and the order will be set correctly.

How is alodine applied?

By immersion — the parts are dipped into the solution, which is why it is described as a rapid and low-cost process. Closed cavities and deep blind features trap air and stay untreated, so they have to be vented.

Get your alodine quote

Upload a STEP, IGES or PDF drawing. Tell us the aluminium alloy, the colour you need, and the full process route if the part is also being machined, welded or anodized.

Get a quote Machine it first

What to send us

Drawing — 2D and 3D files (STEP, IGES or PDF).
Alloy — the aluminium grade, so the conversion reaction can be judged.
Colour — clear or gold.
Process route — machining, welding, anodizing: the order has to be set correctly.
Closed features — any sealed cavity or deep blind hole that the solution cannot reach.
Quantity — number of units, including any spares.

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