Hard chrome is a functional coating, and the bath behind it has never been the fast part of an electro plating line. This brightener is built to change that balance. It is a single-catalyst additive for hexavalent chromium baths that raises cathode efficiency, so a larger share of the current you pay for becomes deposit instead of hydrogen, and the layer reaches a wear thickness in a fraction of the time a conventional hard chrome bath needs.
KCR-25 suits wear work rather than appearance work: hydraulic rods and cylinder bores, moulds and dies, pump shafts, rolls, guide rails, wear plates, and the reclamation of worn or undersized parts that have to be rebuilt to size with a hard, low-friction surface.
The bath is chromic acid with a sulfuric acid addition, and the brightener is the only other plating chemical it needs. There is no second component to keep in ratio with the first, which matters on a line where the same bath runs for weeks — one consumption figure to watch and one container standing at the tank.
Deposit quality starts before the tank. Degrease, rinse, activate and rinse as usual, and make sure the part enters the chrome bath with a clean, unbroken water film; a chrome layer will not cover for a poorly prepared surface. After plating, hard chrome parts are normally ground or lapped back to final tolerance, so the hardness and the crack structure of the deposit are what make that finishing step, and the service life behind it, predictable.
If you are weighing up a conversion from an existing hard chrome plating process, tell us the parts you plate, the steel you plate them in and the thickness you are aiming for, and we will confirm whether this bath fits or point you to another additive in the range.
| Component | Operating range | Standard |
| Chromium trioxide | 200–275 g/L | 250 g/L |
| KCR-25 Catalyst | 20 ml/L | 20 ml/L |
| Sulfuric acid | 2.5–4 g/L | 2.7 g/L |
| Temperature | 50–60 °C | 58 °C |
| Cathode current density (Dk) | 50–75 A/dm² | 60 A/dm² |
| Anodic current density | 15–30 A/dm² | 30 A/dm² |
Every metal plating process has a point it is happiest at, and the standard column above is where we suggest you start: the middle of each window, with headroom on both sides so a correction never means rebuilding the bath. Charge the tank with roughly two thirds of the final volume of water, add the chromium trioxide and let it dissolve fully under circulation, then add the sulfuric acid, and only then the catalyst. Bring the bath to temperature before the first part goes in.
Where you sit inside the chromic acid window changes how the bath behaves. A leaner bath favours efficiency and deposition speed. A richer bath carries current more evenly over a complex part and stays steadier at high current density. Which end suits you depends on the geometry you plate most: deep recesses and long bores generally want the richer side, simple shafts and flat plates the leaner side.
Chrome baths evaporate, and evaporation is the most common reason a bath drifts out of specification when nobody has added anything. Top up with water to the working level, circulate, and take a Baume reading before you add more chromium trioxide. The density chart further down this product converts that reading into a chromic acid figure at both 15 °C and 60 °C, and those two numbers are not the same.
Keep the sulfuric acid and the catalyst as two separate decisions. They are separate plating chemicals doing separate jobs, and a sulfate figure that has drifted will look like a brightness problem long before anyone suspects the acid.
A hard chrome bath does much of its own heating. At the current densities this process runs at, the rectifier puts a substantial heat load into the tank, and on a busy line the problem is usually cooling rather than heating. That is why temperature is a control problem here, not a set-and-forget number.
Temperature is also the variable that moves first in most metal plating processes when something drifts, so hold the whole tank at one temperature rather than the spot where the probe happens to sit. A bath that reads correctly at the thermocouple but runs cooler at the far end plates unevenly, and the difference shows up as thickness variation along a long part before it shows up on any gauge.
Both heating and cooling capacity are needed. Heat exchangers and cooling pipes in titanium, Teflon or other fluorocarbon materials resist chromic acid, and the fluid inside those pipes has to keep moving at all times, or the bath stratifies and the exchanger fouls. An automatic controller earns its place on a bath of this type: an operator watching parts cannot also be watching a thermometer.
Where you sit inside the window also shifts the balance between brightness and crack structure — running hotter tends to give a brighter, more open deposit, running cooler a harder, more closely cracked one. Pick a point, hold it, and treat any change of setpoint as a change to the deposit you qualified.
| Current density (A/dm²) | Deposition rate (µm/h) |
| 30 | 20–35 |
| 45 | 40–50 |
| 60 | 50–70 |
| 7.5 | 70–90 |
| Bath the figures describe | KCR-25 catalyst in a chromic acid bath at the recommended operating conditions |
| Trend across the range | A higher current density gives a higher hourly build of chrome |
| Where the higher rates matter | Wear build-up on rods, rolls, cylinder bores, moulds and worn parts being rebuilt to size |
| Spread within a single band | Rack position, agitation and part geometry, rather than a change in the bath itself |
| Chromium trioxide (g/L) | Bath density | Baume at 15 °C | Baume at 60 °C |
| 180 | 1.13 | 16.7 | 16.7 |
| 195 | 1.14 | 17.8 | 15.9 |
| 210 | 1.15 | 18.9 | 17.0 |
| 225 | 1.16 | 20.0 | 18.1 |
| 240 | 1.17 | 21.1 | 19.1 |
| 255 | 1.18 | 22.1 | 20.1 |
| 270 | 1.19 | 23.2 | 21.0 |
| 285 | 1.20 | 24.2 | 21.9 |
| 300 | 1.21 | 25.2 | 22.7 |
Chromium trioxide is a strong oxidizer and a hazardous material, and this bath is built on hexavalent chromium. Treat both with the respect the safety data sheet asks for: sealed containers, a dry store away from reducing agents, organic material, acids and heat, and local exhaust ventilation wherever the bath is open. Chromic acid mist is the main exposure route on an electro plating line, so extraction and personal protective equipment at the tank belong to the process, not to overheads.
Storage and transport follow the same logic. Keep drums closed and dry, do not stack them where they can take water, and keep them away from anything that could start a reaction. For shipment, the classification and paperwork follow the hazardous-goods rules of the destination — tell us the port and the market and we will confirm what the consignment requires before it leaves.
Documentation is handled the same way. The safety data sheet and the technical data sheet for this product are available on request. If your customer or your market asks for a specific declaration, send us the exact requirement and we will confirm what can be supplied for this product rather than leave you to assume it.
If hexavalent chromium is restricted or being phased down where you operate, raise it at the enquiry stage. We supply hexavalent chromium hard chrome chemistry, and the wider range also includes alloy processes positioned as chromium-free alternatives; it is far better to have that conversation before a bath is charged than after.
| Check | KCR-25 hard chrome | CHROME 31 decorative additive |
| Primary job | Wear resistance, dimensional rebuild and low friction | Bright coverage and appearance over a nickel underlayer |
| Deposit build | Built to a wear or repair thickness, then ground or lapped to final size | Thin decorative layer; appearance is the finish |
| Hardness and structure | 950–1100 HV; microcrack network up to 400 cracks/cm | Not specified as a wear layer; chosen for covering power |
| Current density | 50–75 A/dm² | 15–20 A/dm² |
| Bath chemistry | Chromic acid 200–275 g/L, sulfuric acid 2.5–4 g/L, KCR-25 catalyst 20 ml/L | Chromic acid 150–250 g/L, CHROME 31 additive 5–9 ml/L; lower chromic acid load |
| Coverage | Chloride-free bath protects low-current areas from etching | Throwing power raised by 30–60% for complex shapes |
| Parts that fit | Hydraulic rods, cylinder bores, moulds, rolls, guide rails, wear plates | Trim, hardware, sanitary ware and other visible parts |
| Choose this when | The part has to resist wear or be rebuilt to size | The part has to look bright and fully covered |
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.
The reference figure is two to three times the deposition speed of a conventional hard chrome plating process, and it comes from two things working together: cathode efficiency of 23–26% and the ability to run above 60 A/dm². What that becomes on your line depends on the current density you can actually apply to the part in front of you, so use the deposition rate table as the planning figure and confirm it on a trial part before you quote a cycle time to anyone.
Yes. This process runs in a steel tank lined with PVC or sprayed with vinyl chloride resin, and a lead-lined tank is not suitable. The anodes need the same attention: lead-tin at 93% lead and 7% tin is the recommended grade, with lead-antimony acceptable as an alternative, and auxiliary anodes should match the main anodes.
Micro-hardness sits in the 950–1100 HV range, and the deposit carries a microcrack network of up to 400 cracks per cm. The cracks are intentional — they spread corrosion current over many small cells and hold oil on a running surface — so do not read a cracked deposit as a defect until you have checked it against the specification you set.
Chloride attacks steel where current density is lowest: inside recesses, at bore ends and on the side of a part facing away from the anode. With no chloride in the bath those areas come out clean, which is what lets you put complex parts on the same line as simple shafts. Keep chloride-bearing drag-in low at the same time — rinse properly after acid activation and before the part enters the chrome tank.
No. This is a hard chrome brightener for functional coatings: wear resistance, hardness and dimensional build-up. Decorative chrome depends on a different additive whose job is coverage and appearance over a nickel layer. Tell us which finish you are aiming for and we will point you to the right product instead of letting you trial the wrong one.
Take a Baume reading and correct it for temperature against the density chart in this product. The same bath reads differently at 15 °C and at 60 °C, so a reading taken hot and compared with a cold reference will send you chasing a concentration problem that does not exist. Read, correct, then decide whether to add chromium trioxide or just top up with water.
