This is a brightener for sulfate acid zinc plating — the zinc sulfate and boric acid bath used wherever a metal plating line has to lay down a bright, ductile zinc layer quickly. It is charged at make-up and topped up as the bath consumes it, and it is not tied to a single recipe, so it can go into a bath that is already in production.
Continuous galvanizing is the main home for it: wire, strip and tube travel through the bath at speed, and in a process of electroplating measured in seconds the coating has to form evenly. It also handles rack loads and single workpieces dipped one at a time, which lets a shop running both continuous and job work keep one additive on the shelf.
It sits inside a broad range of acid zinc plating chemicals that also covers potassium chloride systems, cyanide-free alkaline processes, purification agents and the passivation and sealing steps that follow. That matters when a line is being converted or a second source is needed: the chemistry, the dosing advice and the documentation come from one place instead of three.
| Bath type | Sulfate acid zinc, based on zinc sulfate and boric acid |
| Zinc sulfate (ZnSO4·7H2O) | 300–450 g/L |
| Boric acid (H3BO3) | 20–30 g/L |
| SZ-30 brightener | 14–18 ml/L |
| pH | 3.0–4.5 |
| Temperature | 10–50 °C |
| Cathode current efficiency | >95% |
| Anode | 0# zinc ingot |
| Brightener form | Liquid concentrate, measured by volume per litre of bath |
| Monitoring points | pH, temperature, brightener level and zinc content — the four readings that keep the plating process in control |
Bath make-up. Dissolve the zinc sulfate heptahydrate in warm water first and let the sediment settle before you filter or decant. Charging the brightener into a cloudy make-up locks the dirt into the bath. Add the boric acid, bring the volume up, then charge the brightener last and circulate before the first load goes in.
Hold the pH inside the band. The boric acid is there to buffer the cathode film, and pH is the first thing to check when brightness falls away. Acid additions pull it down, while it creeps up as zinc is plated out and drag-out returns rinse water to the tank. A calibrated meter and a short check at the start of each shift catch most drift before it shows on the parts, and they keep the plating process predictable from one shift to the next.
Watch the iron. Pickling carry-over, dropped parts and unbagged anodes all put iron into a sulfate bath. A little is tolerable; a lot takes the brightness out of the deposit, grays the work and clouds the solution. Keep racks dressed, bag the anodes, filter continuously, and when iron still climbs, treat the bath with a purification agent that settles iron without stripping zinc.
Filter and analyse on a routine. Continuous filtration keeps anode sludge and airborne dust out of the deposit; batch filtration is the minimum. Titrate zinc and check pH daily, and keep a simple log of brightener additions against square metres plated so the trend is visible instead of guessed at.
Dosing and consumption. Add brightener by consumption, not by the calendar. Drag-out, part geometry and rinse discipline decide how fast it leaves the tank, so there is no single figure to quote for this grade — track it over your first month and reorder against your own number. Clean final rinses and controlled drag-out do as much for consumption as any dosing rule.
| Wire diameter (mm) | Plated length (m) | Running speed (m/min) | Current per wire rod (A) | What the band suits |
| φ ≤ 1 | 5–8 | 10–30 | 20–80 | Fine wire, run at the highest line speed with the lowest current per rod |
| φ ≤ 2.5 | 10–16 | 7–20 | 120–350 | Mid-size wire, carrying the longest plated length of the three bands |
| φ ≤ 5 | 8–12 | 5–10 | 200–500 | Heavier wire, run slower with the highest current per rod |
| Property | What to establish | How to verify |
|---|---|---|
| Appearance and brightness | Whether the deposit matches the agreed colour and gloss after passivation | Plate a panel at production current density and compare with a retained standard under the same lighting |
| Coating thickness | The zinc weight or thickness your part needs, agreed before the trial | Cross-section, XRF or coulometric gauge; record the current density and line speed used |
| Corrosion resistance | The salt-spray hours required by the drawing, with the passivation and sealing step named | Neutral salt spray to ASTM B117 or ISO 9227; report hours, thickness and passivation type together |
| Adhesion and ductility | Whether the coating survives bending, drawing or wire handling without cracking or peeling | Bend, draw or adhesion test on your own workpiece before a full production load |
| Deposit distribution | Whether edges, recesses and high-current areas stay within the appearance standard | Plate a shaped rack panel or a sample of the real part and inspect high- and low-current areas separately |
| Trial protocol | Whether the additive fits the whole metal plating process, not just the plating tank | Run the sample through pretreatment, plating, passivation and drying, then compare with your current finish |
| Lot-to-lot comparison | Whether a new drum behaves like the last one | Keep a plated coupon from each batch and compare brightness and thickness before releasing the drum to production |
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.
Yes. It is formulated for sulfate acid zinc baths rather than one fixed recipe, so it can be charged into an existing zinc sulfate and boric acid bath — the same approach we take across our acid zinc plating chemicals range. Check the zinc sulfate and boric acid content and bring the pH into range before the first addition, then plate a test piece before you commit a production load. If the bath has been idle or carries heavy iron, filter and treat it first.
Continuous galvanizing and single workpieces are both served by the same additive, which is why it suits lines that switch between coil or wire work and short rack runs. The difference sits in the settings, not the chemistry: running speed and current per wire change with diameter, and rack work moves to a lower current density with a longer dwell. Use the wire setting table for the continuous side and adjust from a test panel for rack loads. Keeping the metal plating process stable across both is mostly a matter of holding pH, temperature and brightener level constant.
By consumption, not by the calendar. Drag-out, part geometry and rinse discipline decide how fast the brightener leaves the tank, so log additions against square metres plated and let your own figures set the dose. Plate a test coupon before and after an addition and compare brightness side by side. Treated that way, the other plating chemicals on the line stay in balance too and the bath stops drifting between corrections.
Usually contamination, or a control point that has slipped. Iron and copper build up from pickling carry-over, dropped parts and unbagged anodes, and they gray the deposit and cloud the bath. Low brightener, pH outside the working band, temperature below the range and weak filtration produce similar symptoms. Work through them in that order — analyse the bath, check pH and temperature, confirm the brightener level, then look at filtration — before changing anything. Ruling contamination out first saves a lot of unnecessary additions on any metal plating line.
Keep drums and containers closed in a cool, dry, ventilated store, away from oxidisers and out of direct sunlight, and keep the safety data sheet with the container. Treat it as an industrial chemical: gloves and eye protection when decanting, and no eating or drinking in the plating area. Ask your sales contact for the safety data sheet and the composition statement that applies in your market, since electroplating chemicals can carry different labelling requirements from country to country.
