Galvanizing Robot: From Sorel's Zinc Bath to ABB

Hot-dip galvanizing protects steel by dipping it in a bath of molten zinc at about 450°C. It is hot, smoky work, and one of the hardest jobs at the kettle is skimming zinc ash and dross off the surface by hand. A galvanizing robot takes over that kind of task. This post traces galvanizing from the first zinc dipping experiments in 18th century France, through the big batch plants and continuous strip lines, to the ABB robots that skim zinc pots on steel lines today, and asks where robots could go next in batch galvanizing plants that still run mostly on cranes and hand tools.

Steel tubes come out of the zinc bath at a hot-dip galvanizing plant while a worker in a face shield watches. Photo: jimpg2_2015 / Wikimedia Commons (CC BY-SA 2.0)

How galvanizers dipped steel by hand

In 1742 the French chemist Paul Jacques Malouin described coating iron by dipping it in molten zinc. The process became practical in 1836, when Stanislas Sorel patented an improved method in France: clean the iron with sulfuric acid, coat it with an ammonium chloride flux and then dip it. The flux keeps the clean surface from oxidising before it meets the zinc. By 1850 the British galvanizing industry was using about 10,000 tons of zinc a year, for sheet, wire, buckets and other goods that had to survive the weather.

Zinc coated ornaments and household goods in a display case at the former Hoesch galvanizing works, LWL open air museum Hagen. Photo: Aquamunda / Wikimedia Commons (CC BY 4.0)

The steps Sorel described still define a batch plant. Steel is degreased in a caustic bath, pickled in acid to remove mill scale, fluxed, dipped in the zinc kettle until it reaches the bath temperature, lifted out and quenched. For most of the industry's history people did all of this with hooks, chains, overhead cranes and long hand tools. Old galvanizing works such as the former Hoesch plant, now kept at the LWL open air museum in Hagen, Germany, show how much of the work depended on people standing close to hot baths and acid tanks.

Inside the former Hoesch galvanizing works, now part of the LWL open air museum in Hagen, Germany. Photo: Aquamunda / Wikimedia Commons (CC BY 4.0)

Automation came first where the product was simple and continuous. On a continuous galvanizing line, steel strip runs from a coil through cleaning, annealing and the zinc pot without stopping, so the dipping itself is done by the line. Skimming stayed manual for a long time. Zinc dross collects on the bath surface and spoils the strip if it is not removed, and a paper on a Chinese dross removal robot notes that people did this work with safety hazards and poor working conditions. Steelmakers abroad had already replaced them with robots, the paper says, and the Chinese robot went into service at Masteel.

A worker skims the surface of a galvanizing kettle by hand while steam rises. Photo: Babalon246 / Wikimedia Commons (CC BY-SA 4.0)

Robots at the zinc pot today

New kettles keep opening. On 22 September 2026, TradeArabia reported that GalvaHub had started hot-dip galvanizing at Metal Park in Abu Dhabi's Khalifa Economic Zones after charging and melting nearly 900 tonnes of zinc. An August report described the 16.2 metre kettle, built for beams, columns, transmission and lighting poles, bridges and towers, holding 610 tonnes of molten zinc at about 450°C, with capacity for 150,000 tonnes of steel a year. In September, POSCO also broke ground on a new automotive steel sheet plant in Gwangyang, South Korea, described in reports as a galvanizing plant.

Galvanized poles hang from a crane beam at the hot-dip galvanizing plant in Sumgayit Technologies Park, Azerbaijan. Photo: Wertuose / Wikimedia Commons (CC BY-SA 4.0)

ABB robots already work at zinc pots on continuous lines. The Italian integrator PRISMA Impianti built robotic slag skimming for the two hot-dip galvanizing lines at ArcelorMittal Taranto. Line 1 uses ABB IRB 4600 robots, and line 2 uses an IRB 4600 and an IRB 6640, each fitted with a custom skimmer at the zinc pot. The cells have safety fencing with interlocks and sensors, and motorised safety fences on the pot open and close automatically. The robot repeats the skimming stroke at the pot, so a worker no longer has to stand over the bath with a hand tool.

An ABB robot seen between the open halves of a die casting die; ABB builds protected Foundry versions of its robots for hot, dirty cells. Photo: ABB

A zinc pot is also hard on the robot, and for places like this ABB sells Foundry Plus 2 versions of many of its arms. They are sealed to IP67, have a corrosion resistant coating and can be cleaned with high pressure steam. ABB robots in this kind of dress have handled hot steel before. At the Teesside Beam Mill in England, two IRB 6400 FoundryPlus robots were installed in 2003 to spray identification codes onto hot beams, a job ABB described as keeping people away from the process, as described in steel mill automation.

One of two ABB IRB 6400 FoundryPlus robots that spray identification codes on hot beams at the Teesside Beam Mill. Photo: ABB

Where galvanizing robots go next

Batch plants are the obvious next target. Kettles like GalvaHub's take mixed loads of beams, poles and fabrications hung on jigs, so every dip is different and most plants still run on cranes and people. A heavy arm such as an ABB IRB 6700 with Foundry Plus protection could skim zinc ash between dips, apply flux or hang and unhang parts at the jigging station. That is a possibility for now, since we found no published ABB batch galvanizing cell. Spin galvanizing of small parts, which AZZ runs on automated conveyor lines with centrifuges, is already closer to a robot cell.

Steel parts hung on jigs below an orange crane beam, ready for dipping at the Sumgayit galvanizing plant. Photo: Wertuose / Wikimedia Commons (CC BY-SA 4.0)

Variety makes this difficult. A pole, a balcony frame and a crate of bolts all need different hooks, dip angles and drain times, and a robot needs a program for each. Engineers can build and test those paths offline in RobotStudio before a robot goes near the kettle, and camera or laser checks could find the bath level and the floating ash. Galvanizers who know how a load drains are hard to replace, and whatever they know has to end up in the robot program.

An ABB IRB 6700 grinding a steel part in Teqram's EasyGrinder cell at Ancofer. Photo: ABB

Then there is money. A robot cell at a kettle needs fencing, protected arms and room on the floor next to a bath that is already crowded, and small galvanizers may not have the volume to pay for it. Against that stand the hazards the Masteel paper lists for manual skimming, from safety risks to poor working conditions, plus burns, fumes and heavy lifting. Homeowners will see little of this, since their fence posts, garden gates and balcony rails come back from the galvanizer looking the same either way.

Workers in hard hats check freshly galvanized steel at a plant in Vojvodina, Serbia. Photo: Government of the Autonomous Province of Vojvodina / Wikimedia Commons (CC BY-SA 3.0)

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