Electropolishing electrolytes

Identity and process boundaries

POLIGRAT lists E 268 and concentrate E 268 K separately. Its E 391 sheet for pure titanium grades 1–3 unexpectedly names E 392 in the application paragraph, leaving that paragraph’s attribution unresolved. E 268 product page Struers describes electropolishing as controlled anodic dissolution and distinguishes electrolytic etching for microstructural contrast. Struers electrolytic preparation

ASTM B912-26 covers passivation by electropolishing and makes the result conditional on alloy, formulation and operating conditions. Chemical brightening, electrocleaning and abrasive polishing have separate process roles. ASTM B912-26 public scope

A supplied electrolyte, a separately supplied concentrate, and a used bath are different material states. POLIGRAT lists E 268 and concentrate E 268 K separately. Its page also states that process liquid contains dissolved metal. Synthesis. The identity and analysis of stock liquid cannot describe every later bath state. A concentrate suffix is part of the product identity, not a package-size alias. POLIGRAT E 268

Exact commercial examples

The examples below establish source-specific identities. They are not interchangeable products or a complete supplier catalog.

Synthesis. A listed alloy family is positive evidence for the named product's intended application. An omitted alloy is an evidence gap, not a proven incompatibility. A grade number without its material family can be ambiguous. These sources do not establish compatibility with coatings, joints, mixed-metal assemblies, or every heat-treated condition.

Ingredient disclosures and formulation limits

ESMA's US SDS revised 30 September 2024 identifies E972 and discloses ethylene glycol, CAS 107-21-1, at less than 50% by weight and 2-hydroxyethyl hydrogen sulfate at less than 50% by weight, with no CAS number supplied for the latter. Its transport section separately names ethylene glycol, sulfuric acid, and phosphoric acid. The ingredient table therefore does not support an inference that other acids are absent. E972 SDS, sections 1, 3, 14, and 16

The older bundle calls the second disclosed ingredient "Glycol Sulfa Ester" and labels the formula a trade secret. That historical name is not silently treated as an analytical identity or a statement that today's formulation is unchanged. 2015 SDS within the E972 bundle

Synthesis. Acids provide acidity and can participate in surface dissolution. Solvents and water form the liquid medium and affect transport. Those broad functions do not assign an undisclosed additive a specific role, identify the rate-controlling mechanism, or establish that a disclosed solvent is the only solvent. SDS ingredient bands are hazard disclosures rather than a manufacturing formula, active-content assay, purity certificate, or lot analysis. Two upper bounds do not determine the balance.

E 391 and E 392 carry a manufacturer claim of freedom from chromic acid. Their sheets do not disclose a full ingredient table or a detection limit. That claim is narrower than absence of all chromium species, absence of substrate-derived metals in used liquid, or a waste classification. E 391 sheet, E 392 sheet

Quantities and measurement bases

These are supplied-product descriptions, not bath control values or operating instructions.

The first three rows refer to the 2024 US E972 SDS.

The historical E972 bundle gives specific gravity 1.24 to 1.49 on the TDS page but 1.38, water = 1, in its attached 2015 SDS. Its TDS describes acidity below 40% without a mass, volume, or acid-equivalent basis. That acidity statement is not a composition calculation. E972 bundle, TDS and SDS section 9

POLIGRAT labels the E 391 value 1.75 to 1.78 g/ml and the E 392 value 1.54 to 1.58 g/ml as "Specific weight/density." The units describe mass per volume, despite the combined label. Neither sheet states a measurement temperature or method. E 391 technical data, E 392 technical data

Synthesis. Weight percent describes constituent mass divided by total sample mass. Volume percent uses a volume denominator and requires its own definition and conditions. Neither equals grams of element per litre or an acid-equivalent result. A hydrated salt's mass and its contained metal mass differ. A reported acid percentage also needs a named acid or equivalence convention. No salt-to-metal or acid-equivalent conversion is established for these products.

Density has units of mass per volume. Specific gravity compares densities at stated reference conditions. Packaging mass divided by nominal package volume is not automatically a measured density. These distinctions prevent a container label, historical typical value, or unspecified test solution from becoming a current-lot property.

Surface outcomes and acceptance limits

ESMA's 14 November 2022 color statement, DOC.006C Rev A, attributes E972's light-amber-to-light-brown variation to acid raw materials. ESMA says that this variation does not affect performance. That statement addresses supplied-liquid color, not the gloss, color, corrosion resistance, or dimensional acceptance of a finished workpiece. Manufacturer color statement

The POLIGRAT sheets describe smoothing, burr removal, and finishes ranging from silky matt to high gloss. They do not supply a complete roughness measurement method, cutoff, trace direction, starting surface, or paired numerical before-and-after roughness results. Synthesis. Their claims do not establish an attainable Ra or Rz, gloss instrument result, dimensional allowance, or uniform material removal on a particular geometry. The application examples do not constitute medical, food-contact, aerospace, or customer qualification. E 391 sheet, E 392 sheet

ASTM B912-26's public scope names 200-, 300-, and 400-series stainless steels and precipitation-hardening alloys. Its conditional passivation discussion does not extend that scope to titanium or turn a supplier claim into demonstrated compliance. Only the public scope supports this reference; paid test criteria are not reproduced. ASTM B912-26, updated 16 June 2026

Source versions and coverage

Reviewed on 30 October 2026 PDT. The ESMA evidence distinguishes an undated TDS with a 2015 SDS attachment, a separate four-page US SDS revised 30 September 2024, and the 2022 color statement. All pages of those files were read. The manufacturer legacy host serves the cited files; corresponding current-host paths returned 404 during review. Availability on the legacy host does not establish that no newer regional revision exists.

The complete one-page English POLIGRAT E 391 and E 392 sheets have no visible issue dates or revision numbers. Their upload-directory date is not a document revision. The E 391 application-name discrepancy remains unresolved. The E 268 and Struers web pages are undated retrieval snapshots. POLIGRAT ingredient SDS coverage remains missing, so no complete chemistry comparison follows.

This reference excludes electrolyte preparation, process settings, bath maintenance, and production recipes. It establishes no current-lot purity, quantitative finish guarantee, environmental acceptance, or customer capability. Related context is available in Surface-finishing processes.