Fengfan Zinc Nickel Alloy Natural Trivalent Chromium Passivation TR-393

Product Overview

Zinc-nickel plating carries the corrosion protection on a part; the passivate decides how much of that protection survives the first winter, the first wash line and the first handling cycle. TR-393 is the immersion stage that closes the gap — a trivalent chromium passivate formulated for zinc-nickel alloy deposits, forming a tight, uniform and transparent film in natural colour over the plated surface.

Because the film is clear, the part keeps the colour of the deposit underneath. It reads as a natural metal finish rather than a dyed or iridescent one, which suits work where the zinc-nickel layer is the finish the customer actually sees: fasteners, brackets, fittings and hardware that get handled, packed and shipped without a topcoat over them.

Running it takes a temperature-controlled immersion tank and a rinse after it, nothing more specialised than that. The working solution is long-lived and simple to maintain, with the parameters adjusted as the bath ages rather than fixed for the life of the tank. In a metal plating process, this is the stage that decides whether a part still looks and performs like new a year outdoors. Construction projects lean on anodized metal for both durability and appearance. Aluminium anodizing is popular for architectural work because it gives a clean finish that stands up to weathering, while alodine coating prepares surfaces for painting so the coating adheres better and lasts longer. Working with an experienced plating partner lets construction firms specify materials that are expected to meet project and building standards, which protects value and client trust over the life of the build.

Process Sequence

1. Zinc nickel plating. The passivate is built for zinc-nickel alloy deposits, so the layer that carries the corrosion performance is laid down first, at the thickness your drawing or your corrosion target calls for.
2. Rinsing. Throughout the process of electroplating, the rinse between two tanks is what carries one bath into the next. Plating bath dragged into the passivate shortens its life and dulls the film, so this rinse is part of the process, not an optional extra.
3. Gloss forming. A short bright dip ahead of the passivate lifts surface brightness, so the transparent film sits over an even surface instead of a dull one.
4. Rinsing again. Same reason as step two — whatever arrives on the part changes what the passivate does to it.
5. Immersing in the passivate. The parts pass through the working solution for the time and temperature set out in the operating window below; this is where the conversion film forms.
6. Rinsing after passivation. This rinse removes drag-out and stops the reaction running on once the part has left the bath. Rinse quality here shows up directly in how even the film looks.
7. Sealing. Where the corrosion target or the customer specification asks for it, a sealing step follows the passivate.
8. Drying. Parts should be dry before handling and packing. Wet parts mark, and the marks are the first thing a customer sees — the last step of the plating process is also the one most often rushed on an electroplating line.

Bath Composition & Operating Window

Passivate Layer & Corrosion Performance

• Transparent natural colour. No dye and no iridescent tint: the film is clear, so the part reads as the zinc-nickel surface it actually is, with the brightness of the deposit still visible underneath.
• Tight and uniform. The film follows the geometry of the part — threads, edges, recesses and the inside of a barrel load — instead of pooling in one area and thinning in another.
• A reaction layer, not an added coat. It forms on the alloy surface rather than building up on top of it, so close-tolerance features and thread fits stay where they were.
• The protection compounds. Corrosion performance belongs to the plating process as a whole: the zinc-nickel underneath does the heavy lifting, while the passivate slows the attack on that layer and holds the surface through handling and storage. The two together decide how long the part lasts, not the passivate alone.
• What moves the number. Salt-spray hours are not a fixed property of the passivate: they move with the zinc-nickel thickness, the sealing step and how evenly the film formed, so any single figure would only be true for one set-up and one part.

Trivalent Chemistry & Handling

Trivalent chromium only. The passivate is built on trivalent chromium and contains no hexavalent chromium. That is the question a zinc nickel plating company is asked most often by its own customers, and here the answer sits in the chemistry: what goes into the tank is trivalent.

What it changes on the shop floor. Hexavalent passivation brings its own handling regime and its own waste-treatment route with it. Moving the passivation stage of the process of electroplating onto a trivalent product takes that hazard out of the daily running of the line, and the rinse water leaving the tank follows the acidic rinse route rather than a hexavalent reduction step. Have your EHS team confirm local discharge limits for the chemistry before the change-over — those limits are site-specific and cannot be set from a product sheet.

Handling the working solution. At a working pH around 3.5 the bath is acidic, so gloves, eye protection and ordinary acid-handling practice apply when making up, analysing and topping up. Ask your sales contact for the current safety data sheet for the batch you receive and keep it with the line documentation.

The rinse after the passivate. Because the chemistry is trivalent, that rinse carries trivalent chromium rather than hexavalent. If the plant still runs both chemistries, keep the two rinse streams apart so the waste routes stay the way your EHS team planned them.

Storage. Keep containers closed and upright in a cool, dry, ventilated place, out of direct sun and away from heat sources. Bunded storage is worth arranging wherever acidic plating solutions are kept on site.

Bath Control & Maintenance

1. Make up and check before the first part. Bring the concentration into the working window and confirm pH before production starts. In any metal plating process a fresh bath and a well-used one do not behave identically, which is why the parameters are adjusted as the solution ages rather than fixed once and forgotten.
2. Analyse on a rhythm you can keep. Concentration and pH drift first, and they drift quietly. A daily titration on a busy line, with the figure written down, is worth more than a weekly check nobody acts on.
3. Set pH before topping up. Adjusting pH after a top-up mixes two changes into one reading. Correct the pH, bring the concentration up, then read the bath again.
4. Hold the temperature steady. A bath running cool forms the film slowly; one running hot wastes solution and shortens its life. Whatever point in the window you pick, keep it stable across the shift.
5. Watch the drag-out. Consumption tracks how much solution leaves the tank on the parts. A sudden rise usually means more carry-over from the previous rinse, a heavier part mix or a leak — not that the product has become weaker.
6. Keep the bath clean. Plating bath dragged in from the zinc-nickel plating tank, shop dust and particles from the parts all end up in the film. A filter loop on the tank, where the layout allows one, keeps the film even between analysis intervals.
7. Log what a shift needs to reproduce. Concentration, pH, temperature, time, and how the first parts of each shift looked. When a customer asks why one batch looks different, that log is the only answer you will have.

Industry Applications

• Automotive fasteners and underbody hardware. Bolts, brackets, clips and brake-line fittings spend their life with road salt and stone chips. For a zinc nickel plating company, work like this is the everyday case for a zinc-nickel deposit plus a natural-colour passivate: barrel loads, high volume, and a finish that has to survive handling long before it reaches the vehicle.
• Aerospace hardware and spec-driven parts. Where the drawing names a zinc-nickel deposit with a trivalent passivate, the part is accepted against the specification rather than against a sample. Send the call-out and the acceptance test with your enquiry and the match can be confirmed before the first batch.
• Electronics and instrumentation parts. Connector shells, shielding cans and instrument frames need a conductive steel base with a corrosion-resistant surface. A clear film keeps the part looking like metal, which matters on visible hardware and on anything inspected under a bench light.
• Construction and architectural fittings. Brackets, anchors, hinges and visible fixings live outdoors for years. Here colour consistency across a production run counts as much as corrosion resistance, because the parts end up side by side on the same facade and any drift between batches is visible from the ground.
• Industrial equipment and hydraulic components. Parts around process chemicals, washdowns and heat take the passivate as the last stage before assembly. In a metal plating process that is the stage the customer judges, because corrosion starts at a thread or a scratch long before it shows on a flat face.

Stages Either Side of the Passivate

• The zinc-nickel deposit. Our alkaline zinc-nickel process, Eco Zinie 300, is the plating stage this passivate is designed to follow. Building the deposit and the passivate together means thickness and film are chosen as one specification instead of being matched afterwards.
• Gloss forming before it. The bright dip ahead of the passivate is what the transparent film sits on. If the gloss stage is inconsistent, the passivate will faithfully show it, so treat the two as one finish rather than two separate operations.
• Rinse water. Carry-over from the plating tank is the most common reason a passivate bath ages early, and the cause is cheaper to fix than a new bath.
• The rest of the line. Pre-treatment, plating solutions, passivation, sealing and coating all sit in the same range. When a customer specifies a complete finish rather than a single step, the stages can be ordered together and arrive with matching parameter conventions.
• One supplier across the line. Fengfan has worked in surface finishing since 1984, from Wuhan, and the range runs from pre-treatment chemistry through plating, passivation, sealing and coating. That is practical rather than decorative: the process of electroplating a zinc-nickel part can be planned from one source instead of three suppliers whose operating windows do not quite line up.

Ordering & Delivery

Film Appearance & Deposit Fit

Colour comes from the deposit.

The film is clear and transparent, in a natural colour, with no dye and no iridescent tint of its own. The part therefore keeps the colour of the zinc-nickel plating underneath: a bright deposit reads bright, a matte or barrel-finished surface reads matte, and a batch that looks uneven is usually showing unevenness in the deposit and the gloss stage rather than in the passivate.

A heavy film reads slightly warmer.

Concentration, pH, immersion time and bath temperature decide how much film forms. Run heavy and the shade drifts a little warmer and yellower; run lean and it stays cooler and more silver. Both sit inside what buyers accept as natural colour, but once a shade has been approved, hold the bath at one point in the working window and check the first parts of every shift against the approved sample.

Thickness follows the reaction, not a dial.

The layer forms by converting the alloy surface rather than building up on top of it, so its thickness follows concentration, time and temperature instead of being set to a figure. Where a drawing or an end customer calls out a film weight or thickness, send that call-out with your enquiry: we will confirm what can be measured and reported for the batch you receive, rather than quote a number measured on someone else's part.

Sealing deepens the look.

Where a sealer follows the passivate it adds gloss and can deepen the shade a little. Judge colour after the full sequence — deposit, gloss dip, passivate, seal — because that combined finish is what the customer opens the box to.

Which deposits it accepts.

TR-393 is formulated for zinc-nickel alloy deposits from both alkaline and acid zinc-nickel baths. Plain zinc is a different substrate and the range holds separate products for it. If you are not certain what your line lays down — the nickel share in particular — send a plated sample with the enquiry and the fit can be confirmed before a tank is made up.

Salt Spray Evidence & Test Conditions

Film Defects & Cold Baths

1. Read the bath as it actually ran — concentration, pH, temperature and dwell taken from the shift log rather than the set points. A bath that has drifted out of the window is the first and most common cause of a patchy film, and it is the cheapest to rule out.
2. Look at the rinse before the passivate. Plating solution carried in on the parts consumes the bath and leaves streaks and dull patches; check rinse flow, when it was last changed, and whether parts drain before they go in.
3. Check how the load sits. Parts touching in a barrel, flat faces nesting together or work hanging against a jig leaves areas the solution never reaches. Re-space the load and see whether the same faces come out patchy again.
4. Then look upstream at the gloss stage. A film this clear shows whatever is underneath, so an uneven bright dip or a trace of oil comes through as uneven colour rather than as a fault in the passivate.
5. Only now adjust the window — dwell first, one change at a time, with a first-off part kept from each shift so the cause is confirmed rather than guessed.
6. Running at the cold end is a working condition, not a tolerance. 25 °C is the bottom of the window and a legitimate production point, though a cool bath forms the film more slowly, so the compensation is time rather than concentration: extend the dwell and hold it there.
7. Never pair a cool bath with a short dwell. That combination is how thin, patchy, under-coloured films happen, and it is why some plants conclude the tank must be heated when it only needs longer. On a line with no heating, watch what actually moves the temperature: overnight and winter ambient, cold make-up water, and the first load of the morning — record the bath temperature at the start of each shift and insulate or cover the tank if winter room temperature drops below the window.
8. If the film blisters, flakes or powders off, stop adjusting the passivate. That behaviour points back to the deposit or the rinse, and no change in this tank will fix it.

Exceptional Durability and Corrosion Resistance

Fengfan's zinc nickel plating is built for parts that have to keep working in demanding conditions. The coating resists corrosion and wear, which makes it a practical choice for industries that cannot afford early failures. Electroless nickel plating adds a uniform layer across complex geometry, so recessed areas and edges receive the same protection as flat surfaces. That consistency extends the working life of components, reduces maintenance costs and gives buyers confidence in long-term performance.

Technology for Enhanced Performance

Innovation at Fengfan centres on how the plating process is controlled, not just on the metal being deposited. Electroplating techniques and alodine coating are tuned to improve surface finish and durability, while anodizing aluminum and aluminium anodizing are used where a harder, more uniform oxide layer is needed. Each process is matched to the part's base material and its end use, so the finish supports the job it has to do. Share your drawing, base material and required finish with our team so the right process and tolerance can be confirmed before production.

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.

FAQ