Fengfan's trivalent chromium black zinc passivation agent is a post-treatment for alkaline zinc plated parts. It produces a dark, shiny black conversion film on the zinc surface, giving fasteners, brackets, stampings and small assemblies a deep black finish without a dye step. The chemistry is single-component, so the bath is built and maintained from one addition rather than a multi-part system. The film is designed to be sealed when the job calls for longer salt-spray life; the sealer forms an additional protective layer over the black passivation. This fits an industrial metal plating process that already runs alkaline zinc and wants a controlled black post-treatment. It is not a black paint, dye or plating deposit; the colour comes from the reaction between the passivation bath and the zinc layer. Confirm the zinc deposit, part geometry and sealing requirement on your own trial parts before setting the line.
| Parameter | Value |
|---|---|
| Operating condition | Recommended range |
| TR-127 concentration | 100 ml/L (recommended); 80-150 ml/L (operating range) |
| pH value | 1.8 (recommended); 1.5-2.2 (operating range) |
| Passivation time | 60 s (recommended); 30-60 s (operating range) |
| Temperature | 25-35 °C |
| Substrate | Alkaline zinc plating |
| Coating appearance | Dark and shiny black |
| Component | Single-component passivation solution |
| Hexavalent chromium | Not contained |
| Other harmful metals such as silver | Not contained |
| Sealing | Can be used with a sealing agent to improve salt spray and corrosion resistance |
| Brand | Fengfan |
| Place of origin | China |
The black colour is a conversion film, not a dye, so the base zinc deposit has a direct effect on the final look. A clean, well-rinsed alkaline zinc layer gives the passivation a better chance of an even dark tone. Part geometry matters as well: recesses, blind holes and rack contact points can hold solution or dry unevenly, leaving patches that are visible after sealing. Sealing is the main lever for corrosion performance. Used after rinsing and before drying, a sealing agent adds a protective layer over the black film and can lift salt-spray resistance beyond the passivation alone. The sealer also affects gloss and can shift the colour slightly, so check the final appearance with the sealer you intend to use rather than judging the passivation before sealing. If the film looks grey, thin or uneven, check the zinc deposit first, then the passivation concentration, pH, time, temperature and rinse quality. A dull zinc layer, a drifting bath or a slow rinse can all show up as a poor black. Keep trial records for each part family, because the same bath can behave differently on a flat stamping and a deep-drawn bracket.
Fengfan also supplies aluminum anodizing chemicals and process support for customers who finish aluminum parts alongside zinc-plated steel. Anodizing is a different metal plating process: it grows an oxide layer on aluminum rather than depositing a metal. That oxide layer improves corrosion and wear resistance and gives a base for dyes and sealers. If a project includes both anodized aluminum and black passivated zinc, keep the two finishes on separate lines and confirm the colour match under the same lighting. Our anodizing range covers the anodizing step itself; the black passivation agent described here is for zinc. For anodizing lines, ask for the separate process data and trial support. We can also discuss how anodized parts and electroplating steps are sequenced when both appear in one assembly.
Zinc nickel plating is a different substrate from alkaline zinc. If your parts are plated with a zinc-nickel alloy, this black passivation agent is not the right match; use a black passivation developed for zinc-nickel. The distinction matters because the nickel content in the alloy changes how the passivation reacts, and a bath made for alkaline zinc will not give the same black tone or corrosion result. For industrial metal plating lines that run both zinc and zinc-nickel, keep the two passivation baths separate and label the tanks clearly. Zinc nickel plating is often chosen for higher corrosion targets, especially in automotive and outdoor hardware. When your finish specification calls for black on zinc-nickel, ask our team for the matching zinc-nickel black passivation and its own operating data. Do not judge the zinc-nickel finish by a trial run in the alkaline zinc bath.
| Item | Detail |
|---|---|
| Payment | 100% T/T in advance |
| Order quantity | Varies by chemical; confirmed with our sales team per order |
| Lead time | 2 weeks |
| Packing | 10 kg/box; 25 kg or 50 kg/bag; 20 kg/25 kg/30 kg/200 kg/drum; 1000 kg/IBC drum |
| Shipping | Per the terms agreed in the current contract |
| Warranty | Inspection certificate issued after delivery stating the batch number and warranty period |
| Customization | Share your requirement with our sales team; we will confirm what is possible for the chemical and order |
| Wholesale pricing | Quoted per order for bulk volumes; contact our sales team |
| Details to send | Bath system, substrate, part geometry and sealing requirement |
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.
It comes after zinc plating and rinsing, and before sealing and drying. The zinc deposit must be clean and fully rinsed first. If the zinc surface is dull or stained, fix that before passivation, because the black film cannot hide a poor zinc layer.
It is designed for alkaline zinc plating. It is not intended for zinc-nickel alloy deposits; zinc nickel plating needs a black passivation made for that alloy. Confirm your zinc system with our team before running the bath.
No. Nothing in this process deposits metallic nickel. The bath is a trivalent chromium passivation, and what forms on the part is a conversion film: the chemistry reacts with the zinc already sitting on the surface and rebuilds it into a black chromate layer. A nickel plating bath works the other way round — metal ions in the solution are reduced and build a new metallic layer on top of the part. That difference decides how you specify, inspect and rework the finish.
Several practical consequences follow. Because the film is formed from the substrate rather than added to it, it is far thinner than a plated metal layer and does not build up on threads, bores or close-tolerance features, so the dimensional result is set by your zinc thickness, not by the black step. The finish can also only be as uniform as the zinc beneath it: a thin, dull or poorly adherent alkaline zinc deposit will show through the black film, and passivation will not hide plating defects. Where a drawing specifies zinc nickel plating or a nickel underlayer, treat this product as a different substrate question rather than a substitute, and confirm it with us before you run a trial.
If your customer's specification calls for a declared nickel-free statement, ask us for the technical data sheet and safety data sheet for the batch you receive and have the wording confirmed in writing, rather than relying on the general point that the step is non-nickel plating. Buyers supplying skin-contact, automotive or electronics chains often need that document trail filed alongside their own test results.
Rework follows a different route as well. The black film is a surface conversion on zinc, not a bonded metal deposit, so stripping and re-passivating is not handled the way nickel stripping is — ask us for the recommended procedure before anyone improvises at the tank. For effluent planning, pass the bath composition documentation to your treatment contractor so they can confirm which discharge limits apply to your line.
Yes. A sealing agent can be used after rinsing and before drying. Sealing is the usual way to push salt-spray and corrosion resistance further. Follow the sealer's own concentration, pH and drying instructions, because the sealer controls the final gloss and protection.
The zinc deposit, part geometry, rack or barrel loading, rinse quality and drying all affect the final look. A part that traps solution or dries slowly can show patches or drag marks. Run a trial part with the same rack or barrel arrangement you will use in production.
Check the zinc deposit first, then the passivation pH, concentration, temperature and immersion time. Contamination and poor rinsing can also dull the black. Bring the bath back into its recommended window before adding more chemical, and compare against a known-good trial part.
It is designed for alkaline zinc plating. Acid zinc has a different deposit and bath chemistry, so confirm with our team before using it on an acid zinc line. A trial on your own parts is the only reliable way to judge the black tone and corrosion result.
Run a side-by-side trial on the same zinc-plated parts. Compare black tone, film uniformity, adhesion after drying, salt-spray result with your sealer, and how the bath holds pH and concentration over a production shift. Keep the trial records; they are more useful than a visual check on a single part.
