Fengfan Bright Zinc Alkaline For Rack And Barrel Plating ZN 50

Product Overview

Bright zinc plating for lines that want cyanide out of the tank. This alkaline zinc plating solution is built for plating shops that run rack work and barrel work from the same order book and want one chemistry they can hold steady. Deposits come out bright across a wide cathode current density range, so a part sitting on the high-current edge of a jig and a part tucked into the low-current centre can leave the same tank looking alike. The zinc layer distributes evenly over uneven surface areas and holds on with especially good adhesion.

The process is organised around the things that decide whether an alkaline line stays stable: controlled agitation, continuous filtration, local exhaust ventilation, nickel-coated steel anodes and carbonate management. Every one of those requirements is written out below, so a shop can walk the line and check it before the first drum goes in. That check is usually the difference between a clean changeover and a week of chasing defects when a metal plating process is moved off cyanide in a hurry.

Process Advantages

• Bright deposits across a wide current density range. Parts at the high-current edge of a rack and parts in the low-current centre can come out with the same brightness, which means fewer selective re-racks and less touch-up.
• Excellent metal distribution. A load that mixes brackets with small pins and threaded parts gets a more even zinc thickness, so the shop does not have to run a separate setting for every shape on the order book.
• Especially good zinc-layer adhesion. The deposit stays where it is put through racking, unloading and the handling that follows, and it accepts a chromate or passivate film without lifting at the edges.
• One chemistry, two line types. Rack plating and barrel plating can both run on this system, which keeps buying, bath analysis and operator habits on a single set of routines instead of two.
• Built for post-treatment. The bright zinc layer can be chromated or passivated straight after plating, so the colour and corrosion performance you sell is decided in the next tank rather than inside the process of electroplating.
• Cyanide out of the line. Removing cyanide changes how the bath is handled, ventilated and treated as waste, so plan the conversion with our technicians before the old bath is drained.
• Requirements published up front. Tank lining, ventilation, agitation, filtration, anodes, heating and carbonate control are all specified, so the plating equipment can be checked against the list before a single drum is opened.

Technical Data

Tank Line & Equipment

• Tanks: rubber-lined steel, PP or GFK with a polypropylene liner. An alkaline zinc bath attacks mild steel, so the liner is the first piece of plating equipment to inspect before the bath goes in — particularly on a tank that previously ran acid zinc plating chemicals. Look at the seams and the coating, not just the tank walls.
• Local exhaust ventilation: required. An alkaline zinc tank releases a fine mist at the surface, and the ventilation is part of how the line is run rather than an optional comfort item.
• Part and electrolyte agitation: both required. Solution movement across the surface of the work is what keeps the deposit even and stops the zinc from depleting in the boundary layer.
• Electrolyte agitation: 1–2 turnovers per hour. Enough to keep the plating solution uniform without pulling air into it.
• Part agitation: 2–4 m/min for rack work. This is the travel of the work through the bath, and it sets how quickly fresh electrolyte reaches the surface.
• Barrel rotation: 3–6 rpm. Fast enough to turn the load over, slow enough that parts do not climb the barrel or abrade each other.
• Filtration: required, at approximately 2 bath turnovers per hour. Continuous filtration removes the particles that would otherwise show up as roughness on a bright deposit.
• Precoat-type filter: polypropylene with an alkali-resistant filter aid. Filter media containing cellulose must not be used — cellulose breaks down in an alkaline bath and feeds the breakdown products straight into the solution you are trying to clean.
• Zinc dissolving tank: have the construction and dimensioning of the zinc dissolving compartment and baskets done with Fengfan field technicians, because the geometry has to match your tank and your zinc consumption.
• Carbonate freezing unit: required for reducing the carbonate content in the electrolyte. Carbonate accumulates in every alkaline zinc bath, and the freezing unit is how the line keeps it from taking over the working window.

Use Scenarios

Alkaline zinc sits behind a lot of ordinary hardware: brackets, fasteners, hinges, welded tube frames, stamped sheet parts, and cast or forged components that need a corrosion-resistant finish before painting, powder coating or assembly. Shops with a mixed order book tend to settle on it because it is a metal plating process that carries a small turned pin in a barrel and a long welded frame on a jig without a chemistry change.

It suits plants moving off cyanide, and it suits plants that have been running acid zinc plating chemicals and now need better coverage on parts with recesses, blind holes or folded edges. Acid systems are efficient and bright on flat work; the alkaline route earns its place where the shape is awkward and the deposit has to reach inside it.

Typical users are job plating shops, captive finishing lines in hardware and automotive supply, and metal plating plants that run zinc alongside nickel, copper or passivation. Large parts and low volumes point to rack work; a drum of small parts supports the barrel.

Rack Zinc Plating

1. Pick the contact point first. Put the jig contact on a face that will be hidden or machined after plating, because a bright zinc deposit keeps a contact mark permanently and the mark always sits where the current entered.
2. Space the parts so solution can move between them. A crowded rack throws shadowed areas that plate thin, and no amount of brightness on the exposed faces makes up for a thread root that never saw fresh electrolyte.
3. Watch where the current lands. Edges, corners and thread crests sit at the top of the current density range while recessed faces sit at the bottom, and the wide window of this bath is what lets both ends run in the same load.
4. Strip and re-coat racks on a schedule. Zinc builds up on the rack coating and on worn contact tips, and that build-up quietly changes how the current divides across the load.
5. Keep the work moving. Part movement is what carries fresh solution into recesses and sweeps hydrogen away, and it is the part of the process of electroplating operators change most often when a rack starts plating unevenly.

Barrel Zinc Plating

Barrel plating is the volume end of the work. Screws, nuts, washers, small stampings, pins and clips are cheaper to tumble than to jig, and the same plating process that handles a welded frame on a rack handles a full drum of them. The load makes contact through the barrel's internal contacts, the barrel turns slowly enough to keep the parts tumbling and presenting fresh surfaces, and solution exchanges through the perforations on every revolution.

What barrel work rewards is judgement about the load, not a different chemistry. Overfill the barrel and the parts nest, contact turns erratic and the deposit varies from the front of the drum to the back; underfill it and the parts rub against each other instead of tumbling. Very large flat parts, heavy components that damage each other on impact, and parts whose faces have to stay unmarked are better off on a rack — the same rule that holds for any metal plating bath, and the reason many shops keep both routes running. If you have been buying acid zinc plating chemicals for barrel work and coverage inside the load is the recurring problem, this is the route to compare against.

Post-Treatment Preparation

1. Rinse immediately. The plating process is not finished when the rack or barrel leaves the zinc tank, and alkaline electrolyte carried over on the parts will contaminate the next tank long before anyone notices the deposit is wrong.
2. Clear any alkaline film. A short acid dip, where the line uses one, lets the passivate react with the zinc instead of with the residue sitting on top of it.
3. Chromate or passivate while the deposit is fresh. The bright zinc layer accepts chromate and passivate treatment readily, and it is that next tank, not the zinc bath, that decides the final colour and the corrosion performance your customer sees.
4. Rinse and dry with clean water and clean air. Water spots and drying marks read as plating defects on a bright zinc surface even when the deposit underneath is sound.
5. Inspect the load before it leaves the line. Check recesses, thread roots and contact points, and compare the appearance against the sample that was approved.

Bath Make-Up & Operating Window

The figures on this product come from laboratory work and production-line practice; treat them as a starting point rather than a fixed recipe. Actual values are adjusted to the material and geometry of the parts, the application the finish has to survive, and the conditions of the plating plant. Make-up concentrations, working temperature, cathode current density and plating time are set per bath, because a drum of small washers and a jig of welded tube do not want the same window.

Send us the tank volume, the base material, whether the work runs on racks or in a barrel, the zinc thickness you have to reach and where the goods are going, and our technicians will confirm the make-up and replenishment figures for your line. After that, replenishment follows bath analysis rather than a calendar, which is how a plating solution stays inside its window instead of drifting to one edge of it. The process of electroplating zinc from an alkaline electrolyte turns on how much zinc metal and brightener are in the tank at any moment, so the analysis schedule matters as much as the first charge.

Ordering & Delivery

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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