Identifying steel through the furnace: labels that survive 500 °C and acid baths

In steelmaking, the identification has to outlast the process — not just the warehouse. Here is how to keep the part number legible after the furnace, the pickling bath and the galvanising line.

In most industries a label only has to survive storage and shipping. In steelmaking it has to survive the process itself: annealing and heat-treatment furnaces, hot-dip galvanising, and pickling baths with 25–30% hydrochloric acid. A standard adhesive label chars, curls or simply dissolves long before the part reaches dispatch — and with it goes the traceability of the coil, the billet or the bar.

The mistake is to look for "a more resistant sticker". Above roughly 150–200 °C, or in an acid bath, no pressure-sensitive adhesive holds. The reliable approach is to split the problem in two.

For extreme heat and chemicals, the answer is a hang tag with no adhesive: the tag travels with the part, fixed mechanically through a reinforced hole such as wire, clip, bolt or hook, so there is no adhesive to fail. Two materials cover this range. A polyimide film (Lit-Off HOT 150/151) withstands up to 450–500 °C in short exposures — the same family used in electronics and aerospace — and is ideal for parts that go through the furnace. A Kraft/PET/Kraft laminate (Lit-Off KPK 842/800/874) handles up to 200–350 °C depending on thickness, and it resists the 25–30% hydrochloric acid of pickling and galvanising baths, the case where heat and acid combine in the same line.

For moderate high temperature on a smooth surface, an adhesive polyester is enough. For cold coil, sheet or painted structure that sees up to +200 °C, a high-temperature acrylic adhesive polyester (Lit-Off 820) keeps a clean adhesive label with full barcode legibility.

In every case the print is done by thermal transfer with resin ribbon, so barcodes, 2D DataMatrix and EN 10204 cast traceability stay readable after granulation, UV and machining oils.

At Lit-Off we manufacture these labels and tags to size — rolls, fanfold or die-cut — and supply industry across Spain and Portugal, with a free technical sample and a reply within 24 hours so you can validate the material on your own line before committing.