Glass melting electrode

molybdenum

Product overview
Molybdenum glass melting electrodes for electrically heated glass tanks are engineered to withstand extreme thermal loads and aggressive glass melts. Plansee electrodes are produced by special forging and forming processes to provide a smooth surface, coarse-grained creep-resistant microstructure and excellent straightness to minimise deformation, wear and downtime.

Your advantages at a glance

• Minimum 99.97% Mo purity for bubble-free application
• Optimised electrical and thermal properties
• High creep resistance
• Excellent corrosion resistance
• Oxidation protection via Sibor® coating
• Standard products from stock and customer-specific solutions

Molybdenum-zirconium dioxide (MoZrO2) electrodes
For particularly aggressive glass melts, MoZrO2 electrodes (molybdenum with small ZrO2 additions) offer improved corrosion resistance and better creep performance than pure molybdenum. MoZrO2 reduces corrosion caused by aggressive refining agents (e.g., Sb and As oxides) and is especially effective in coloured container glass melts.

Sibor® — oxidation protection
Molybdenum oxidises above ≈400 °C. The Sibor® coating protects Mo up to ≈1700 °C by forming a hard, dense diffusion barrier and an SiO2 surface seal. Depending on operating temperature, Sibor® can provide protection for up to several thousand hours and allows electrode mounting prior to tank heating.

Low corrosion ensures a long service life
Low material removal rates in service are crucial for long electrode life and influence final glass quality. Plansee molybdenum exhibits low corrosion rates in most glass melts.

Highest quality from a single source
Plansee manufactures electrodes from raw material to finished part in-house using only high-purity feedstock (min. 99.97% Mo, metallic purity without W) to avoid discolouration and bubble formation.

Composition and impurities (summary)
Material: Mo (molybdenum) minimum content: 99.97% (metallic purity without W). Guaranteed / maximum impurity values (µg/g): Al 10; Cr 20; Cu 20; Fe 20 (typ. up to 100); K 20; Ni 10 (typ. up to 50); Si 20 (typ. up to 100); W 300; C 30 (typ. up to 100); H 10; N 10 (typ. 20); O 40 (typ. 70); Cd 5; Hg 1; Pb 5.

Plansee standard dimensions and threads (summary)
Diameter [mm (inch)] — Diameter tolerance [mm] — Surface quality — Straightness (mm per 1 m) — Recommended cylindrical thread — Recommended taper thread
31.75 (1.25") — +/- 0.3 — Fine forged — < 2.0 — M18, M22, 7/8-14 UNF — 1-8 UN 3" TPF
48 mm — +/- 0.3 — Fine forged — < 1.5 — M22, M24, 7/8-14 UNF
50.8 (2") — +0.0 / -0.8 — Fine forged — < 1.0 — M24, M27, 1 1/4-12 UNF — 1 9/16-8 UN 3" TPF
54 mm — +/- 0.4 — Fine forged — < 1.0 — M27, M36, 1 1/4-12 UNF
60 mm — +/- 0.4 — Fine forged — < 1.0 — M27, M36, 1 1/4-12 UNF
63.5 (2.5") — +/- 0.4 — Fine forged — < 1.0 — M36 — 1 15/16-8 UN 3" TPF
70–101.2 mm (3"–4") — tolerances and straightness vary (typ. +/-0.4 to +/-1.0; straightness < 1.0–2.5 mm) — Fine forged — recommended larger metric or UN threads (see table for details)

Available services & customisation

• Standard sizes in stock
• Custom dimensions on request
• Mechanical machining, special threads, cooling ducts
• Coating (Sibor®) and customer-specific solutions

Characteristics / technical specifications

• Material options: Molybdenum (Mo) and MoZrO2 (Mo + ZrO2 additions)
• Purity: ≥ 99.97% Mo (metallic purity, without W)
• Typical impurity maxima (µg/g): see Composition and impurities
• Surface: fine forged, particularly smooth
• Straightness: typically <1.0 mm to <2.5 mm per 1 m depending on diameter
• Recommended threads: metric and UN variants depending on diameter (e.g., M24, M27, M36, 1 1/4-12 UNF, 1-8 UN 3" TPF)
• Application: electrodes for electrically heated glass tanks, including aggressive melts when using MoZrO2