Anodizing cold-seal formulations
Supplied cold-seal chemicals for anodized aluminium, with exact-product ingredient disclosures, conditioned reference properties, and sealing-test limits.
Tags: chemicals, anodizing, surface-finishing
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Identity and scope
SurTec describes 350 as a liquid cold seal free of nickel, cobalt and chromium, and lists fluorides. 354 lists nickel, cobalt and fluoride salts. Neither sheet identifies the exact salts or their percentages. The nickel-free description gives no detection limit. SurTec 354, pp. 1 and 4 The same portfolio classifies 351 Hardwall separately as dye fixation with a subsequent seal. SurTec 350 SurTec anodizing portfolio
The examples describe supplied liquids and powders. SurTec 650 is listed separately for passivation of anodized surfaces. SurTec portfolio
"Cold" identifies a product or process class, not permission to use any ambient conditions. The technical documents below describe different chemistries and qualified treatment sequences. This article gives reference properties rather than bath preparation, operating settings, or a treatment recipe.
Exact-product comparison
These are examples, not interchangeable grades or an exhaustive catalog. Ingredient classes below describe the extent of the technical disclosure, not a complete formulation. Dates are printed document dates, rather than upload-path dates.
| Supplied product and document | Disclosed identity and constituents | Evidence boundary |
|---|---|---|
| SurTec 354, German technical sheet, 14 July 2022, five pages | Liquid cold seal. The ingredient section lists nickel salts, cobalt salts, and fluoride salts. | Individual salt identities, hydration states, and constituent percentages are absent. SurTec 354, pp. 1 and 4 |
| SurTec 356 Hardwall, alias Hardwall 3 CB/1, German technical sheet, 8 December 2022, four pages | Powder cold seal. The ingredient section lists nickel salts. | No particular nickel salt or complete recipe is identified. A separate bath fluoride measurement does not supply a powder fluoride assay. SurTec 356 Hardwall, pp. 1–3 |
| SurTec 350, German technical sheet, 23 May 2022, four pages | Liquid fluoride cold seal. Ingredient classes are inorganic salts and fluorides. Described as free of nickel, cobalt, and chromium. | No elemental detection limits or salt identities. The claim does not mean fluoride-free. SurTec 350, pp. 1 and 4 |
| ANODAL CS-2N Powder, Reliant technical sheet, revised 2 June 2015, two pages | Powder for room-temperature sealing. The sheet identifies nickel and fluoride and describes nickel-fluoride-based sealing. | No concentrate ingredient-percentage table, CAS identities, hydrate assignment, density, or solids assay appears. ANODAL CS-2N, pp. 1–2 |
The global portfolio names SurTec 356 IT Hardwall as a nickel-fluoride-based powder with a cobalt-free color-correction system. That suffix is absent from the 356 Hardwall sheet above. The portfolio also calls SurTec 372 Hardwall a concentrated liquid cold seal with a cobalt-free color-correction system. Neither description supplies a composition assay for the differently named 356 Hardwall product. SurTec portfolio
Supplied-product reference properties
The values retain the sheets' central values and parenthetical ranges without assigning an unreported statistical meaning. All three tables are headed at 20 °C. Liquid pH entries refer to concentrate, abbreviated "Konz." in the source. Powder pH refers to a specified test solution, not dry powder or a working-bath target.
| Exact material | Appearance | Density at 20 °C, g/mL | pH under the stated test condition | Source |
|---|---|---|---|---|
| SurTec 354 | Clear green liquid | 1.036, range 1.02–1.06 | Concentrate 5.6, range 5.3–5.8 | 354, p. 4 |
| SurTec 354 F, companion fluoride-salt solution | Clear colorless liquid | 1.072, range 1.05–1.09 | Concentrate approximately 6.3 | 354, p. 4 |
| SurTec 350 | Clear colorless liquid | 1.029, range 1.01–1.04 | Concentrate 5.4, range 5.1–5.6 | 350, p. 2 |
| SurTec 350 A, companion aluminium-salt additive | Clear colorless liquid | 1.023, range 1.01–1.03 | Concentrate approximately 12.8 | 350, pp. 2 and 4 |
| SurTec 356 Hardwall, Hardwall 3 CB/1 | Greenish-red powder | Not reported | Approximately 5.5 at 10 g/L | 356 Hardwall, p. 2 |
SurTec 350 also lists the same SurTec 354 F properties shown above. The companion additives are separate supplied products. Their listing does not establish their presence in unopened main concentrate. The sheets give no total-solids percentages.
Composition and measurement bases
The sheets distinguish nickel-based product analysis from free-fluoride analysis. Synthesis from these separate measurements is that product amount, nickel content, and free-fluoride content are different quantities. A nominal chemical formula does not establish measured free fluoride in solution. SurTec 354, pp. 2–3, SurTec 356 Hardwall, p. 3
The following distinctions are dimensional and chemical interpretation, not additional product specifications.
- Mass percent of a salt, mass percent as nickel, and mass percent as fluoride have different numerators. Hydrated and anhydrous salt masses also differ. Metal-equivalent conversion needs the exact formula, hydration state, assay, and reporting basis. These ingredient-class lists do not supply them.
- Mass per volume, such as g/L or mg/L, differs from mass fraction. A ppm value needs its analytical basis before conversion to either quantity.
- Percent by mass means component mass relative to mixture mass. Percent mass per volume and percent by volume use different denominators. Density relates the mass and volume of the same material at a stated temperature. Density alone does not reveal solids or active-species content.
- Concentrate pH and test-solution pH describe different samples. Neither establishes an actual bath's pH, stability, or sealing result.
An SDS is a hazard-communication document. For example, OSHA's mixture disclosure requirements address health-hazard ingredients and permit ranges under specified conditions. Such a list need not account for every formulation ingredient. A concentrate SDS range is not a working-bath recipe or performance certificate. No exact-product SDS was verified for the compared formulations in this research. OSHA SDS Appendix D, section 3
Sealing quality and test applicability
Manufacturer test claims concern treated coatings, with their process conditions and post-treatment history. SurTec 356 qualifies its quality-control discussion by including subsequent ageing treatment. ANODAL CS-2N makes its test claim conditional on the recommended procedure. Neither is a lot-specific test report or proof that composition alone establishes pore closure. SurTec 356 Hardwall, p. 2, ANODAL CS-2N, p. 1
Public standards scopes describe measurements and limits, not universal acceptance values.
| Public edition and measurement | Scope limitations relevant to interpretation |
|---|---|
| ISO 2143:2017, edition 3, dye absorption after acid pretreatment | Excludes deep colors, coatings below 3 µm, dichromate seals, supplementary oil, wax, or lacquer treatments, and alloys above 2% copper or 4% silicon. Less appropriate for hydrothermal seals with nickel salts, cobalt salts, or organic additives. ISO 2143 scope |
| ISO 2931:2017, edition 4, electrical admittance | Applies to aqueous sealing. Results from different sealing methods are not necessarily comparable. Also limits comparisons for alloys above 2% silicon, 5% manganese, or 3% magnesium. Requires sufficient test area and thickness above 3 µm. Acceptance use depends on anodizer-customer agreement. ISO 2931 scope |
| ISO 3210:2025, edition 5, destructive mass loss in phosphoric-acid-based solution | Distinguishes methods with and without prior acid treatment and their intended applications. Excludes normally unsealed hard-type coatings, dichromate-only seals, chromic-acid anodizing, and hydrophobic treatments. Hydrothermal-sealing methods can be appropriate to other seals. Replaces ISO 3210:2017. ISO 3210 scope and edition |
These are public scope summaries, not procedures or paid acceptance tables. Undated standard references in older manufacturer sheets do not establish testing to these editions. No numerical results, lot traceability, or complete customer qualification records accompany the compared property tables.
Applicability and evidence limits
SurTec 350 qualifies its alkaline-resistance claim with a footnote referring to separate information sheets. Those unverified details prevent a universal chemical-resistance rating here. SurTec 350, p. 1, footnote 1
Synthesis from these document boundaries is that a product name, ingredient list, and concentrate properties establish neither a pore-sealing mechanism nor a completed ageing state. They do not guarantee corrosion resistance, dye-bleed resistance, adhesion, food-contact or medical suitability, environmental acceptability, wastewater compliance, or customer acceptance. "Nickel-free," "cobalt-free," and "chromium-free" remain scoped manufacturer descriptions. Without an analytical method and detection limit, they are not zero-element assays. A hexavalent-chromium-free statement would concern an oxidation state, not total chromium.
Coverage consists of the complete dated technical sheets above and public manufacturer portfolio and standards scopes, checked on 29 October 2026 PDT. Exact constituent percentages, salt hydration states, total-solids assays, batch certificates, and independent sealing-test results remain unreported or unverified. Regional product names and document revisions remain separate evidence.
Related references
Surface-finishing processes, nickel acetate sealing formulations, and anodizing dyes cover adjacent subjects. These related references are unpublished in the source catalog at this review date.