In the HYDRA project a core focus has been assessing how hydrogen affects product quality, recognizing that environmental gains must align with economic viability for manufacturers.

Highlights on High temperature oxidation

• Carbon Steel

  • Short high‑temperature exposures are similar to pure iron oxidation, forming wüstite, magnetite or hematite depending on temperature (above/below 570 °C) and reaction kinetics.

  • Prolonged exposures lead to irregular scale, blistering, and weakened oxidation resistance. Alloying elements effect and scale adhesion were characterized.

• Stainless Steel

  • Chromium concentrates inside the scale, retarding substrate oxidation; nickel, less prone to oxidize can be found as metal particles in the scale.

  • Resulting scale exhibits Cr‑rich and Fe‑rich layers, with silica and nickel traces strengthening adhesion.

• Electrical Steel

  • Silicon—even at low levels—forms a tightly adherent interfacial oxide. At higher Si, fayalite (Fe₂SiO₄) develops, further anchoring scale.

  • Above 1,177 °C (fayalite’s eutectic point), molten fayalite penetrates grain boundaries, greatly enhancing scale adhesion. Below that, the scale shows classic iron‑oxide stratification, a fayalite/mixed‑oxide interlayer on the base metal.

Implications for the Steel Industry

• Quality Control: Understanding scale morphology enables more precise descaling strategies, improving surface quality.

• Process Optimization: Insights into temperatures and alloying element effects guide heat‑treatment recipes that optimize surface oxidation.

By exploring the thermodynamic and kinetic aspects of scale formation across steel grades, the HYDRA project aims to define hydrogen‑based processing—enhancing sustainability in steel production.