Key takeaways
- Select the base steel against the rod's load path, section size, delivery condition, thread or attachment details, repair philosophy, and required evidence—not by a familiar grade nickname.
- C45/C45E and SAE 1045, or 42CrMo4 and SAE 4140, have overlapping families but different controlling standards and ranges; approve substitutions explicitly.
- Keep base-bar diameter, pre-plate diameter, coating thickness basis, and finished rod diameter as separate order fields.
- Specify engineering chromium requirements under the selected coating standard, including required pretreatment, thickness, adhesion, porosity, post-treatment, inspection, and repair rules where applicable.
- Only accepted order terms define the requirements for a specific supply.
Select the base-steel route from the complete rod duty
A chrome layer does not compensate for an unsuitable core, weak thread transition, inadequate straightness, wrong heat-treatment condition, or damaged pre-plate surface. Start with the cylinder or machine duty: axial load range, compression and buckling case, side load or misalignment, stroke and support length, thread or eye geometry, impact or fatigue concerns, operating environment, seal system, repair route, and consequence of failure. Engineering review remains the buyer's responsibility; JOTAIN can support material and processing coordination against the accepted RFQ.
Medium-carbon C45/C45E or SAE 1045 routes may be reviewed when the design and condition support the required core properties and manufacturability. Chromium-molybdenum 42CrMo4 or SAE 4140 routes may be reviewed when the design calls for a different hardenability, strength-toughness, section-size, or heat-treatment route. That is not a universal ranking. A poorly specified alloy bar can be less useful than a fully defined carbon-steel route, and higher strength can increase sensitivity to surface, thread, heat-treatment, and hydrogen-related controls.
State whether the order is for black or bright base bar, peeled or turned bar, ground plating stock, an unplated machined rod, or a finished plated rod. Those scopes allocate dimensional responsibility differently. For base-bar supply, the downstream plater owns later stock removal and coating controls. For a finished rod, the supplier scope may need to include machining, heat treatment, straightening, polishing, cleaning, plating, post-treatment, final inspection, marking, and protected packing. Do not let the quotation use 'chrome rod' without a boundary drawing and a responsibility list.
The grade designation must include its controlling standard and edition. CK45 is often used commercially as a route label, but the accepted order should identify whether the technical requirement is C45 or C45E under ISO 683-1 or another specified national/product standard. SAE 1045 chemistry comes from SAE J403, while SAE 4140 chemistry comes from SAE J404. Similar names do not authorize substitution, and chemistry alone does not define the supplied mechanical properties.
Compare chemistry and property bases without claiming equivalence
The table below condenses standard ranges for RFQ screening. It is not a substitute for licensed standards or a design calculation. ISO mechanical-property entries apply only to the stated +QT diameter bands and associated standard conditions. SAE J403 and J404 are chemistry standards, so the table does not invent a universal SAE 1045 or 4140 mechanical range. When a purchaser orders a different product form, condition, size, specimen basis, or standard, use that controlling requirement instead.
C45 and C45E share the listed ISO composition ranges but differ in phosphorus and sulfur limits. The purchaser should identify the intended designation rather than writing C45/CK45/1045 as though it were one grade. Likewise, 42CrMo4 and SAE 4140 overlap closely but have different manganese, chromium, molybdenum, phosphorus, and sulfur limits in their cited standards. A heat can satisfy one designation without automatically satisfying the other.
Mechanical-property screening must retain section size and condition. The ISO +QT values shown below change between diameter bands. For a rod outside those bands, for a machined ruling section, or for a different heat-treatment route, the buyer should state the applicable product standard and agreed test basis. Core behavior, surface hardness, induction-hardened layers, weld repairs, or finished-part fatigue are not established by these bar values.
| Grade / designation | Controlling composition standard | Chemical composition range (mass %) | Typical mechanical-property basis for screening | Buyer interpretation |
|---|---|---|---|---|
| C45 / C45E, +QT, d >16–40 mm | ISO 683-1:2016 | Both: C 0.42–0.50; Si 0.10–0.40; Mn 0.50–0.80; Cr ≤0.40; Mo ≤0.10; Ni ≤0.40; Cu ≤0.30; Cr+Mo+Ni ≤0.63. C45: P/S ≤0.045. C45E: P ≤0.025, S ≤0.035. | For the stated +QT band: Rp0.2 ≥430 MPa, Rm 650–800 MPa, A ≥16%, Z ≥40%, KV ≥15 J. | Identify C45 or C45E, ordered condition, diameter band, specimen and impact basis; do not substitute SAE 1045 by name alone. |
| C45 / C45E, +QT, d >40–100 mm | ISO 683-1:2016 | Both: C 0.42–0.50; Si 0.10–0.40; Mn 0.50–0.80; Cr ≤0.40; Mo ≤0.10; Ni ≤0.40; Cu ≤0.30; Cr+Mo+Ni ≤0.63. C45: P/S ≤0.045. C45E: P ≤0.025, S ≤0.035. | For the stated +QT band: Rp0.2 ≥370 MPa, Rm 630–780 MPa, A ≥17%, Z ≥45%, KV ≥15 J. | The size-band change matters; confirm whether bar diameter or another ruling-section convention controls the order. |
| 42CrMo4, +QT, d >16–40 mm | ISO 683-2:2016 | C 0.38–0.45; Si 0.10–0.40; Mn 0.60–0.90; Cr 0.90–1.20; Mo 0.15–0.30; P ≤0.025; S ≤0.035. | For the stated +QT band: Rp0.2 ≥750 MPa, Rm 1000–1200 MPa, A ≥11%, Z ≥45%, KV ≥35 J. | Use only when the design, section size, heat treatment, toughness, machining, and coating controls support this route. |
| 42CrMo4, +QT, d >40–100 mm | ISO 683-2:2016 | C 0.38–0.45; Si 0.10–0.40; Mn 0.60–0.90; Cr 0.90–1.20; Mo 0.15–0.30; P ≤0.025; S ≤0.035. | For the stated +QT band: Rp0.2 ≥650 MPa, Rm 900–1100 MPa, A ≥12%, Z ≥50%, KV ≥35 J. | Do not carry the smaller-diameter values into a larger rod or altered ruling section without the controlling standard basis. |
| SAE 1045 | SAE J403_202402 | C 0.43–0.50; Mn 0.60–0.90; Si 0.15–0.35; P ≤0.030; S ≤0.035; reported residual limits include Cu ≤0.20, Ni ≤0.25, Cr ≤0.20, Mo ≤0.06 for the standard 1045 route. | J403 controls chemistry; it does not give one universal mechanical-property range for every 1045 bar condition and diameter. | Pair J403 chemistry with the product specification, delivery condition, size, heat treatment, testing, and required properties. |
| SAE 4140 | SAE J404_200901 | C 0.38–0.43; Si 0.15–0.35; Mn 0.75–1.00; Cr 0.80–1.10; Mo 0.15–0.25; P ≤0.035; S ≤0.040. | J404 controls chemistry; it does not give one universal mechanical-property range for every 4140 bar condition and diameter. | Define the separate product and property standard; do not certify 42CrMo4 equivalence from family resemblance. |
This table condenses chemistry and selected ISO +QT size bands for RFQ screening. Confirm licensed editions, product scope, condition, ruling section, sampling, impact test details, and product specification. Only accepted order terms define the requirements for a specific supply.
Separate the base-bar specification from the coating specification
The base-steel order should define the product standard, grade, condition, size, straightness, surface route, machining allowance, mechanical tests, inspection document, and traceability. The coating order should define the engineering chromium designation or specification, substrate condition, surfaces to plate or mask, thickness basis and measurement locations, preparation, undercoat if any, adhesion, porosity or other examination when required, stress-relief or hydrogen-embrittlement treatment requirements, finishing, repair, sampling, and acceptance. One document may contain both scopes, but it should not blend them.
ISO 6158:2018 covers electroplated chromium coatings for engineering purposes on ferrous and non-ferrous substrates, with or without undercoats, and provides a designation route that can include coating thickness. ASTM B650-23 covers engineering chromium coatings on ferrous substrates and includes requirements across topics such as classification by thickness, appearance, stress relief or hydrogen-embrittlement treatment, thickness, adhesion, porosity, workmanship, and packaging. Use the coating standard selected by the design or customer; do not combine clauses casually or imply that naming hard chrome fills every order field.
Define whether thickness is a minimum, range, nominal with tolerance, or local requirement under the selected standard and drawing. State where it is measured, whether edges, ends, threaded zones, transition radii, ports, or masked regions are included, and what happens after final polishing. Diameter is affected by coating on both sides of a cylindrical rod, but the contractual calculation and measurement method must follow the accepted drawing and coating specification. Keep pre-plate size, as-plated size, and final polished size distinct.
High-strength steel routes require deliberate treatment of cleaning, residual stress, hydrogen-related risk, and any pre- or post-coating heat treatment required by the governing specification. Do not invent a bake temperature or time from a generic guide. Provide the actual material condition and strength or hardness basis to the responsible coating engineer, then state the agreed treatment, timing, records, and restrictions in the order.
Control the process chain and inspect the final acceptance state
A rod can have compliant chemistry and still fail the purchasing objective because of heat-treatment distortion, insufficient cleanup stock, grinding damage, plating defects, poor masking, local thickness variation, polishing loss, handling damage, or incomplete traceability. Freeze the process sequence before quotation: cut, heat treat, straighten, rough machine, peel or turn, grind, polish, clean, plate, post-treat, final polish, inspect, preserve, and pack. Delete operations that are outside scope and name the party responsible for each remaining step.
Straightness should be inspected in the final agreed state, using the drawing's datum, support, gauge length, rotation, excluded end zones, and frequency. Diameter needs defined measurement positions and temperature or stabilization rules if the tolerance makes them relevant. Surface texture needs a stated profile parameter and evaluation basis; visual appearance is not a substitute. Local dents, scratches, pits, grinding marks, uncoated areas, nodules, burns, or edge effects need an acceptance rule tied to seal travel and functional zones.
Keep base-material and coating evidence traceable to the same rod or lot. The dossier can include the base MTC, heat-treatment report, mechanical or hardness results, dimensional and straightness report, pre-plate inspection, plating batch identity, thickness readings, adhesion or porosity results when specified, post-treatment record, final surface report, nonconformance closures, and packing list. The inspection-document type does not prove the separate coating results unless those records are expressly included.
Issue a quotation line with no hidden scope transfer
The example below shows how to expose material, process, coating, and inspection boundaries. It intentionally leaves drawing-controlled values as references rather than inventing them. A real RFQ should attach the latest drawing, coating specification, inspection plan, and packaging instruction. Require the supplier to identify every process it performs, every subcontracted operation, and every requirement it cannot confirm before order acceptance.
Normalize bid scope before comparison: base bar, unplated ground rod, and finished plated assembly are different supplies. Reconcile condition, processing, coating, inspection, documents, packing, and exclusions line by line.
If the purchaser permits a material alternative, require a written deviation package naming the proposed standard and edition, chemistry, condition, section-size property basis, heat-treatment route, dimensional effect, coating-process implications, inspection changes, and responsible design approval. Do not accept 'equivalent to CK45' or '4140 same as 42CrMo4' as the substitution record.
Base material: C45E to ISO 683-1:2016, or 42CrMo4 to ISO 683-2:2016 only if listed as a priced alternative; supplier to state product standard, exact designation, heat route, and deviations.
Delivery condition: Ordered +QT condition and size band per drawing HR-221 Rev F; heat treatment before final straightening and grinding; MTC and heat-treatment batch traceability required.
Plating scope: Finished engineering chromium plated rod to ISO 6158:2018 and coating specification CP-09 Rev C; supplier to list preparation, masking, undercoat if any, thickness basis, post-treatment, finishing, repair, and subcontracted scope.
Finished diameter: Pre-plate, as-plated, and final polished diameters, tolerances, measurement locations, straightness, texture, functional zones, and excluded end features exactly as HR-221 Rev F.
Inspection: Base chemistry/properties, final dimensions and straightness, coating thickness map, adhesion and porosity checks only as CP-09 requires, final surface inspection, heat-to-rod and plating-batch traceability, and approved nonconformance closures.
Documents and packing: Indexed dossier before release; protected plated surfaces, compatible separators and wrap, capped ends, agreed maximum bundle mass, and destination handling marks.
Supplier response: Identify proposed route, operations performed or subcontracted, sampling, achievable values, exclusions, alternatives, and every deviation with the quotation.Chrome plated rod material selection before RFQ buyer questions
Which steel is used for chrome plated rods?
C45 or C45E and SAE 1045 medium-carbon routes, plus 42CrMo4 and SAE 4140 chromium-molybdenum routes, are commonly reviewed. None is universally correct or automatically equivalent. Selection depends on the controlling standard, condition, section size, load and buckling case, thread geometry, toughness or fatigue needs, machining, straightness, plating process, inspection, and design approval.
What should buyers specify before chrome plated rod quotation?
State the exact base-steel standard and grade, product form, condition, size and mechanical-property basis, process sequence, pre-plate and finished diameters, straightness, texture, coating standard and designation, thickness and measurement, masking, post-treatment, coating inspections, traceability, dossier, packaging, destination, and drawing revisions. Separate required values from supplier proposals.
Is base bar selection enough for chrome plated rod sourcing?
No. A compliant base bar does not establish machining quality, final geometry, prepared-surface condition, coating thickness, adhesion, porosity, post-treatment, polishing, local damage, or packaging. Allocate responsibility for every step and require final-state evidence linked to the same heat, rod or lot, and plating batch.
Chrome plated rod material selection before RFQ RFQ checklist
- Final application, load and buckling case, support length, side-load or misalignment, environment, and consequence of failure
- Base-steel product standard and edition, exact grade designation, allowed substitution route, and design approval owner
- Product form, ordered diameter and length, delivery condition, section-size or ruling-section basis, and required properties
- Heat treatment, straightening, machining, peeling or turning, grinding, polishing, cleaning, plating, and post-treatment sequence
- Supplier, subcontractor, plater, purchaser, and inspector responsibility for each process and release point
- Pre-process, pre-plate, as-plated, and final polished diameters with tolerances and measurement locations
- Straightness datum, support, gauge length, excluded end zones, frequency, and final inspection state
- Surface-texture parameter, evaluation basis, direction, functional zones, isolated damage, and visual acceptance
- Engineering chromium standard, designation, thickness basis, measuring locations, masking, undercoat, and repair rule
- Required pretreatment, stress-relief or hydrogen-embrittlement treatment, timing, records, and prohibited shortcuts
- Coating thickness, adhesion, porosity, appearance, surface, and other tests only as required by the accepted specification
- Base MTC, heat-treatment report, mechanical or hardness evidence, dimensional and coating reports, and dossier index
- Heat-to-rod and plating-batch traceability, marking, nonconformance closures, and purchaser release
- Compatible surface protection, separators, end caps, lifting points, bundle mass, wrapping, storage, and destination
- Quotation scope comparison, subcontracted work, proposed sampling, exclusions, alternatives, and deviations
References
- ISO 683-1:2016 Heat-treatable steels, alloy steels and free-cutting steels — Part 1
Supports: Official standard record for direct-hardening non-alloy steels including the cited C45 and C45E chemistry and size-banded quenched-and-tempered property basis.
Limitation: The catalog record and condensed table do not replace the licensed edition, product scope, delivery condition, specimen rules, or an application design review.
- ISO 683-2:2016 Heat-treatable steels, alloy steels and free-cutting steels — Part 2
Supports: Official standard record for alloy steels for quenching and tempering including the cited 42CrMo4 chemistry and size-banded quenched-and-tempered property basis.
Limitation: The cited ranges do not prove finished-rod properties, coating performance, automatic equivalence to SAE 4140, or fitness for a specific cylinder.
- SAE J403_202402 Chemical Compositions of SAE Carbon Steels
Supports: Official SAE record for carbon-steel chemical-composition ranges, including the cited SAE 1045 chemistry basis.
Limitation: J403 chemistry does not provide one universal mechanical-property range, product condition, dimensional requirement, or chrome-plated rod performance guarantee.
- SAE J404_200901 Chemical Compositions of SAE Alloy Steels
Supports: Official SAE record for alloy-steel chemical-composition ranges, including the cited SAE 4140 chemistry basis.
Limitation: J404 chemistry alone does not define mechanical properties, heat-treatment response, finished rod geometry, coating quality, or equivalence to 42CrMo4.
- ISO 6158:2018 Metallic and other inorganic coatings — Electrodeposited coatings of chromium for engineering purposes
Supports: Official scope for engineering chromium coatings on ferrous and non-ferrous substrates, with or without undercoats, and a designation route that can include thickness.
Limitation: The public scope does not supply a universal coating thickness, substrate grade, polishing allowance, acceptance plan, or cylinder-rod service requirement.
- ASTM B650-23 Standard Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
Supports: Official scope for engineering chromium coatings on ferrous substrates, including classification and requirements addressing thickness, adhesion, porosity, treatment, workmanship, and packaging.
Limitation: The standard must be applied with the actual substrate, strength, drawing, coating class, optional requirements, sampling, and acceptance terms of the order.
Revision note: Expanded on 2026-07-19 with standard-cited C45/C45E, 42CrMo4, SAE 1045, and SAE 4140 ranges plus separate ISO and ASTM engineering-chromium order controls.
Inquiry support
Send part route, grade, condition, inspection needs, and destination.
JOTAIN can review the stated grade, size, delivery condition, processing route, inspection requirements, and export details against the project requirement.