Fengfan AL-100 Aluminum Alloy Trivalent Chromium Passivator

Product Overview

This is a concentrated trivalent chromium passivator for aluminum and aluminum alloys. Diluted with deionized water, it reacts with a clean aluminum surface and forms a clear aluminum conversion coating in seconds to a few minutes, depending on how the line is run. Nothing is electrodeposited: the film grows out of the metal itself, so it follows the profile of the part instead of sitting on top of it.

The step it replaces is the one most shops know as an alodine coating. The chemistry is trivalent chromium with no hexavalent chromium in it, and the line that runs it looks like the line you already have: the same tanks, the same rinses, the same racking.

It is not an anodized coating. An anodic layer is grown electrolytically and measured in microns; this film forms by chemical reaction, leaves the surface looking like aluminum rather than coated aluminum, and can be run immediately before paint, powder coating or adhesive bonding as readily as it can be run as the last tank of the day.

1. Decide where the step sits. The bath runs at the end of an aluminum anodizing process or as a stand-alone tank on bare extrusion and castings, and the sequence below is the same either way.
2. Degrease. Alkaline degreasing for immersion work and for high-silicon castings; acidic degreasing on a spray line.
3. Rinse. Rinse thoroughly — a surface still carrying oxide film or polishing residue will take an uneven film no matter how well the bath is running.
4. Passivate. Immerse or spray at the working concentration and at the time that matches the job. A line already running a chromate conversion coating aluminum process keeps its tanks, racks and rinse stations and changes only this bath.
5. Rinse and dry. The part leaves the line dry and ready to handle.
6. Coat, or leave it. Paint, powder and adhesive can follow as soon as the part is dry; leaving it 24 hours after passivation supports reliable adhesion for a subsequent coating.
7. AL-100 is diluted with deionized water before use, and the equipment should be cleaned thoroughly beforehand. For new channels and new production lines, clean with a 10% sulfuric acid solution first, then rinse thoroughly with water. After that, add the measured AL-100 and deionized water, stir until evenly mixed, measure the pH value and adjust it to 3.9.

Immersion is the standard route and the one most job shops start with. The sequence is alkaline degreasing, a clean rinse, then the passivation tank. High-silicon alloys — which covers most die-cast and many foundry grades — take that same alkaline route rather than the acidic preparation used on a spray line. Parts can hang still on the rack because the bath needs no stirring, and the tank itself can be stainless steel or steel with an acid- and fluoride-resistant lining.

Where an alodine coating tank is already installed, the tank, the rack and the rinse stations stay. Only the bath chemistry and its control range change, which is why most shops convert the step rather than the line.

A job shop that also runs an aluminum anodizing service keeps this as a separate tank rather than a replacement for the anodizing line: parts that need a conversion coating instead of an anodic layer come here, and the two processes sit side by side without sharing chemistry.

• Acidic degreasing is the preparation step. A spray line degreases with acid rather than alkali and then sprays the passivator directly onto the part, which is one tank fewer than an immersion route.
• No agitation in the bath. The concentrate needs no stirring, so a reservoir, a pump and a nozzle set are enough to run the process.
• Built for parts that are awkward to dip. Long extrusions, wide panels and bulky assemblies that would need an oversized tank for immersion are straightforward on a conveyor.
• Measured in seconds. Contact times on a spray line are short enough to sit inside a paint or powder line without slowing it down.
• The same drum serves both routes. A shop starting from an aluminum anodizing kit at small scale can begin on immersion and add a spray station later without changing chemistry.
• An aluminum anodizing service that passivates extrusions before powder coating usually runs this as an inline spray station rather than a batch dip.
• Confirm the nozzle pattern on a scrap panel before the conveyor goes into production.

1. Clean the tank first. New tanks and new lines get a wash with 10% sulfuric acid solution followed by a thorough water rinse; residue from an earlier bath shows up later as a patchy film.
2. Add deionized water and the measured concentrate, stirring as you go. Use deionized water rather than tap water.
3. Stir to a uniform solution.
4. Measure the pH and bring it to 3.9. 5% sulfuric acid solution lowers it, 1% sodium hydroxide solution raises it — add in small increments and re-check after each one.
5. Check the temperature is inside the working band before the first part goes through.
6. Run a scrap panel and inspect the film before the bath goes into production.

Working Bath Ranges

Standard Start-Up Values

• Spray concentration: 250 ml/L.
• Immersion concentration: 200 ml/L.
• pH: 3.9, checked with a meter rather than by colour.
• Spray pressure: 1 bar.
• Open at the standard, not at the top of the range. A fresh bath starts at the standard figure; the 100–500 ml/L band is where you work as drag-out and ageing take the concentration down.
• Dial it in on your own part. Alloy, surface finish and rack loading all move the right number slightly, so confirm the standard against a panel from your line before the first production batch.

Time Selection by Purpose

The bath is asked to do one of two jobs, and they are not interchangeable. As a coating pretreatment the film only has to key the surface for paint, powder or adhesive, and a short contact is enough. As a corrosion treatment the film itself has to carry the corrosion performance, and the part needs longer in the bath.

Because the aluminum conversion coating forms by reaction with the metal rather than by deposition, contact time is the main lever you have over how much film you build. The figures to set on the line sit inside the ranges in the parameter table: by spray, 1 minute for coating pretreatment and 2 minutes for corrosion treatment; by immersion, 2 minutes for coating pretreatment and 4 minutes for corrosion treatment. Those are the optimum points — the ranges around them exist for alloy and loading differences, not for convenience.

Decide the purpose before you decide the time. A bath set up for paint preparation and run at pretreatment times will not deliver corrosion-treatment performance, and a bath run at corrosion-treatment times before powder coating is simply slower for no gain.

Coating Properties

• Low contact resistance. Below 0.8 mΩ/cm², so housings, connector shells and chassis parts can be passivated without losing electrical continuity across a joint.
• Holds up to 100 °C. The corrosion resistance survives a 100 °C exposure instead of decaying at the first hot dry.
• Clear on the part. The aluminum conversion coating is pale and transparent, so anodized aluminum surfaces keep their own appearance instead of taking on a tint. On the sample panels shown with this product — a reflective plate, a brushed plate and a formed shell with a black end cap — the metal still reads as metal; the film adds no colour of its own.
• Does not build like a plated layer or an anodized coating. Threads, fits and machined faces keep their dimensions, and a visual check still shows the surface underneath.
• Meets the standards the drawings call for. MIL-DTL-81706 and MIL-5541 are met or exceeded, tested to ASTM B-117 and DIN 50021 SS neutral salt spray.
• A sound base for the next coat. Paint, powder and structural adhesive bond to the passivated surface, which is why the same bath serves both pretreatment and final finish.

Applications

Most of the work is familiar: parts that used to come off a chromate conversion coating aluminum line go through the same tanks, the same rinses and the same racking, and only the bath chemistry changes.

Parts that leave an aluminum anodizing process and still need a final clear passivation before assembly are handled on the same bath at the same settings, and castings that never see an anodizing line at all go through it just as well.

Electronics and electrical work is the clearest fit: housings, connector shells, busbar and enclosure panels that need corrosion protection without a film that interferes with earthing. Automotive underbody parts, outdoor equipment frames, aerospace fittings and architectural hardware follow the same logic, and anything that will be painted, powder coated, bonded or simply stored outdoors can go through this bath. An aluminum anodizing service that passivates extrusions before powder coating or packing runs it as one more tank on the line.

Bath Control & Consumption

• Analyse on a schedule. Concentration and pH drift with drag-out and evaporation; bring both back to the standard values on analysis rather than topping up by eye.
• Consumption tracks drag-out. Replenishment runs at roughly 15–25 ml of concentrate per m² of work, including what leaves the bath on racks and parts.
• Start from a clean surface. Parts must be free of oxide film before they reach the bath; a water-break check at the rinse station catches most problems before they turn into rejects.
• Sediment in the drum is normal. Stored concentrate can throw a small deposit, and it does not affect quality or performance. Roll the drum before drawing from it.
• The routine does not change with the part. Bare extrusion, castings and anodized aluminum run on the same analysis and the same top-up arithmetic.
• Small baths follow the same rules. A shop running the process from an aluminum anodizing kit controls it exactly like a full line — same analysis, same top-up, same rinse discipline.
• Ask for the SDS with the quotation. It carries the handling, storage and transport classification for the current batch, and the disposal guidance that applies where you operate.

Ordering & Delivery

Coating Appearance & Substrate Compatibility

• Aluminum and aluminum alloys only: AL-100 is built to react with aluminum. It is not the passivator to use on zinc or zinc-nickel plated surfaces, and it will not form the same conversion film on those deposits.
• Zinc-nickel parts belong on a zinc-nickel passivator such as Fengfan TR-393, and zinc-plated parts need the passivator matched to the zinc deposit. Ordering AL-100 for a mixed line and running both substrate types through one tank is the wrong passivator for half the work.
• Keep mixed-substrate racks apart: if a rack carries aluminum parts and zinc-plated parts, passivate them in separate tanks. A shared bath will not treat the zinc surfaces and is not a substitute for the correct zinc passivator.
• Bare and anodized aluminum both fit the same bath: extrusion, castings and parts that have already been through an aluminum anodizing process can be passivated. The step adds a conversion film; it does not replace the anodized coating or the anodizing tank.
• The film is clear and pale, with no dye or pigment in it. Anodized aluminum and mill-finish parts keep their own colour, brush pattern and machined detail, so the part still looks like aluminum after passivation.
• Film thickness is a film weight, not a micron build. Alloy, bath concentration, temperature and contact time all affect how much film forms; if a drawing calls for a film weight, ask for the current data sheet for the batch rather than working from a single generic number.
• Check the alloy before the first production batch. Silicon content and casting method decide the degreasing route and can change how quickly the film forms, so send the alloy designation with the enquiry and we will confirm the starting settings.
• An aluminum anodizing service can run this as a separate tank alongside the anodizing line, in the same way a shop keeps an alodine coating tank separate from its anodizing tanks.

Technical Support & Model Matching

Choosing the right match is where most sourcing decisions stall. As a trading supplier, we keep one point of contact from first enquiry to after-sales: tell us what you are making and the conditions you work under, and we shortlist the closest matches from our supplier network, compare specifications and arrange samples before you commit to a bulk order. If something does not behave as expected, we work with the supplying partner on the cause and a practical fix, and stay with the case until it is settled. Email, WeChat or WhatsApp enquiries get a reply within 24 hours.

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