Electropolishing
Also known as: Electrochemical Polishing, EP, Electrolytic Polishing, Dry Electropolishing, DLyte, Hirtisation
Electropolishing selectively dissolves surface asperities from metal parts by making the workpiece the anode in an electrolytic cell. Peaks dissolve faster than valleys — levelling the surface and reducing Ra without mechanical contact or stress. Three main variants exist for AM parts: (1) Wet electropolishing — immersion in acid electrolyte (typically H₂SO₄/H₃PO₄ for stainless; H₂SO₄/HF for titanium) with DC current; achieves Ra <0.4 µm from Ra 5–10 µm input; (2) Dry electropolishing (DLyte / GPainnova) — solid granular electrolyte medium in a rotating drum; geometry-uniform material removal without liquid waste; (3) Hirtisation® (Hirtenberger) — pulsed electrochemical machining combined with support removal; single-step process for AM internal features.
Why AM parts need this
AM metals have as-built Ra of 5–25 µm (external) and 10–35 µm (internal channels). For medical implants (ISO 10993 biocompatibility), food-contact components (EHEDG), semiconductor parts (SEMI standards), and aerospace hydraulic fittings, Ra must be below 0.4 µm. Electropolishing reaches these targets without dimensional distortion — critical for complex AM geometries where mechanical polishing would round features. DLyte's solid electrolyte variant is particularly suited to AM complex surfaces because the granular medium self-conforms to internal passages and lattice interiors without masking or fixture changes.
Achievable surface finish
Typical input Ra
8 µm
Achievable Ra
0.05–0.3 µm
Wet EP: Ra 0.1–0.4 µm from Ra 2–10 µm input. DLyte from AM as-built (Ra 8–15 µm): Ra 0.5–1 µm in one cycle, Ra <0.2 µm in multiple cycles. Hirtisation on LPBF Ti: Ra 12 µm → Ra 1 µm (single cycle).
Key parameters
Lower: finer finish, slower. Higher: faster removal, risk of pitting on complex AM surfaces.
Stainless steel: 50–80 °C optimal. Titanium: room temperature with HF/H₂SO₄ mix.
Wet EP: 15–30 min typical. DLyte: 30–90 min per batch. Hirtisation: 5–30 min depending on support density.
Per surface. Must be accounted for in critical dimension tolerances. DLyte removes 0.002–0.01 mm per cycle.
From Ra 2–10 µm as-machined input. AM as-built (Ra 10–25 µm) may require preliminary mechanical polishing first.
Compatible AM processes
Compatible materials
Limitations
- Wet EP: requires acid chemistry management, effluent disposal, and COSHH/REACH compliance — not suitable for all shop environments
- Material removal is isotropic — close-tolerance dimensions must be machined AFTER electropolishing
- Deep blind holes may have reduced current density at base — non-uniform finish
- Aluminium alloys require anodising-compatible electrolyte — not the same chemistry as stainless steel
- Copper and copper alloys are not well-served by standard EP chemistry — check compatibility
- DLyte solid electrolyte: limited to workpiece volume <200 mm sphere diameter in current commercial machines
Providers
DLyte (GPX Global)
Spanish developer of DLyte dry electropolishing technology — solid electrolyte-based surface finishing for AM metal parts achieving Ra <0.1 µm without dimensional change. Based in Barcelona.
Barcelona, ES
Poligrat
German electropolishing specialist — Poligrat electrochemical polishing processes for AM stainless steel, titanium, and cobalt-chrome parts to achieve Ra <0.4 µm surfaces for medical, food, and semiconductor applications.
Munich, DE
Hirtenberger Engineered Surfaces
Austrian innovator of Hirtisation® — a pulsed electrochemical machining surface finishing process for AM metal parts that removes support structures and smooths internal channels simultaneously.
Hirtenberg, AT
Aalberts Surface Technologies
Dutch industrial group offering a broad portfolio of thermal, chemical, and physical surface treatments engineered for AM aerospace and automotive parts.
Utrecht, NL
Relevant standards
Ra data from GPainnova DLyte application notes (manufacturer tier) and Hirtenberger published Hirtisation® results (manufacturer tier). Wet EP parameters from Poligrat technical literature. ASTM B912 standards reference.
All post-processing