Overseas wholesale buyers read fast and decide faster. The welding finish you specify determines first‑article approval, repeatability across lots, and total cost of ownership. Treated correctly, finish is a controllable variable that protects margin, secures compliance, and keeps schedules intact. Treated loosely, it becomes the number‑one source of disputes, rework, and returns.
This guide translates shop practices into buyer‑ready language. It draws on ISO 5817 visual acceptance, AWS D1.1 structural guidance, ASTM A380/A967 for stainless post‑weld treatment, and high‑volume export experience at YISHANG. You will find practical targets, RFQ wording, inspection methods, and decision matrices—no fluff, no hard sell.
Buyer Priorities at a Glance
Wholesale procurement teams care about five things: predictable quality, audit‑ready compliance, cost per unit over lifecycle, schedule reliability, and clear responsibilities when things drift. Finish affects all five. A precise callout—class, roughness target, and post‑weld process—reduces risk more than any late‑stage polishing. That is why a simple phrase like “Class B, 63 surface finish, passivate per ASTM A967, inspect at 800 lux” saves weeks later.
Why Finish Drives Performance, Compliance, and Cost
Finish is not cosmetics. It controls stress risers, corrosion pathways, cleanability, and coating adhesion. When working with stainless, welding locally destroys passivity; without pickling or passivation, heat‑tint areas will soon stain. With carbon steel, overly aggressive grinding can tear the surface, leaving marks that show through powder coating. For aluminum, uncontrolled blending can scar the soft base metal and disrupt the uniform color of anodized finishes.
From a compliance standpoint, buyers often reference ISO 5817 for imperfections and pair it with finish language for appearance. For hygiene‑critical zones, surface roughness correlates with soil retention; many programs target Ra ≤ 0.8 µm (≈ 32 microinch finish) on product‑contact stainless. Architectural parts may tolerate Ra ≈ 1.6 µm (≈ 63 finish), while hidden frames accept Ra ≈ 3.2 µm (≈ 125 finish). Linking roughness to zones avoids paying for Class A everywhere.
Cost follows process control. A staged grit path (60 → 120 → 180 → 320) with cooling pauses preserves thickness and lowers scrap. Specifying bead blast surface finish before coating yields uniform anchor profile and reduces orange peel. Clear upstream instructions beat heroic downstream fixes every time.
Microinch ↔ Micrometer quick map
32 µin ≈ 0.8 µm
40 µin ≈ 1.0 µm
63 µin ≈ 1.6 µm
125 µin ≈ 3.2 µm
Finish Classes That Buyers Actually Use (A / B / C)
Class A — Seamless Where Customers Look and Clean Where They Touch
Class A means blended flush, scratch pattern aligned, and no visible shadow lines in typical lighting. In food, pharma, and premium retail, Class A pairs with passivation or electropolishing. When hygiene is a design input, call Ra ≤ 0.8 µm (≈ 32 surface finish) on contact areas and document the measurement method. Be explicit about brush direction on faces and corners. Over‑polishing can thin sections; design for welding by allowing material for blending and using joints that keep neutral axes centered.
Procurement tip: Ask your supplier to state the 2F weld positions used on fillet joints and how corners are fixtured to avoid roll‑over during blending. Confirm that heat tint is removed, not just hidden.
Class B — The Global Workhorse for Visible, Non‑Hygienic Zones
Class B delivers a clean, uniform look without chasing invisibility. Crowns are dressed, spatter removed, grain matched, and discoloration treated. It is the most economical way to protect brand image on retail fixtures, machine guards, and frames that remain visible after coating. For stainless that stays bare, include passivation; for steel that will be coated, define the pre‑treatment—often a bead blast surface finish or power‑tool cleaning to achieve consistent profile.
Useful targets: Visual acceptance at 600–1000 lux, no sharp discontinuities, consistent grain. Roughness typically lands between 40 surface finish and 63 surface finish depending on material and design intent.
Class C — Functional on Hidden Surfaces and Internal Frames
Class C prioritizes structure. Spatter is removed, sharp edges broken, and pores or undercut are unacceptable per ISO 5817, but cosmetic blending is minimal. Use it for internal brackets, enclosed frames, and weldments which will be fully coated. Stainless in condensate zones may still need pickling or passivation even if “hidden.” Write that expectation down.
RFQ snippet: “Internal structure: Class C, remove spatter, break edges. Prep for coating per shop SOP. No arc mark welding scars on visible zones.”
Materials: What Changes and What Must Not Change
Stainless Steel 304 / 316
Heat tint forms where chromium depletes. After blending, restore passivity per ASTM A967 or perform comprehensive cleaning per ASTM A380. In chloride‑rich areas (commercial kitchens, coastal), 316 + electropolish resists staining better than 304 + brush alone. When you state 32–125 surface finish ranges, tie them to zones: 32 in food contact, 63 on decorative faces, 125 on concealed interiors.
Buyer watchouts: Iron contamination from tooling, smeared metal from heavy pressure, and incomplete rinse after passivation. Include verification methods—ferroxyl tests where appropriate and water break‑free criteria before packaging.
Carbon Steel and Galvanized Steel
For steel, finish is about coating performance. Grinding tears or gouges are a liability because powder will telegraph them. Call for uniform profile, consistent radii at edges, and a preparation grade aligned with your system (for example, near‑white blast where specified). Where galvanizing is welded, repair zinc at seams before topcoat. If you want a smooth Class B show face, say so; otherwise a clean Class C is ideal inside the enclosure.
MIG considerations: The advantages and disadvantages of MIG welding on thin sheet include speed and lower operator fatigue, but also higher heat input and potential spatter. Spatter removal time must be planned into the finish budget.
Aluminum
Aluminum oxide melts far above the base metal, so cleanliness, fit‑up, and heat control are vital. TIG gives refined control for visible joints, while pulsed MIG supports throughput on thicker gauge. Plan how the aluminium surface finish will look after anodizing; blended seams can shift color. If the brief demands an aluminium brushed finish or a 63 finish visual, align brush direction early. Where color uniformity dominates, consider powder instead of dye anodizing.
FAQ in one line: Yes, you can you weld aluminum; success rests on prep, heat control, and realistic post‑finish expectations for color.
Copper and Brass
Decorative frames show every heat halo. Lower heat input, shield coverage, and immediate finishing are your allies. Ask “can brass be welded” and you will hear “prefer brazing,” because it preserves appearance and reduces distortion. Where welding is required, expect polishing and sealing to maintain luster.
Alloy Steels: 4130 / 4140 (When You Ship Industrial)
Export industrial programs sometimes specify chromoly. 4130 steel welding demands preheat and controlled cooling; 4130 weldability is good with correct procedure. 4140 weldability is more sensitive due to higher carbon; filler and PWHT policy must be clear. For buyers, the finish callout (often Class C on internal structures) is straightforward, but the WPS/PQR behind it matters more than cosmetics.
Specialty Layers: Make the Substrate Right, Then Add Value
Powder coating over welds solves appearance and durability when the substrate is prepared. Specify uniform profile, edge radius, and clean surfaces. For stainless, a light brush then passivate before clear coat if bare metal is the look. For aluminum, combine a controlled brush with sealing or anodize. Where ultimate hygiene matters, electropolishing stainless welds lowers Ra and enriches chromium, giving easier clean‑down than polish alone.
Do not forget options tied to brand language: a fine bead blast surface finish reads matte and modern; a bright polish reads premium. If drawings show 32‑125 surface finish bands across zones, your supplier can right‑size effort instead of over‑finishing everywhere. That is how metal finishing services and upstream welding assemble into reliable metal finishing solutions.
DFM + RFQ Language: What to Write So Suppliers Get It Right
Design for Welding That Supports Finishing
Corners, access, and heat paths decide finish effort. Large outside fillets near thin faces invite roll‑over when blending. State joint types explicitly—remember a fillet is one of the five basic weld joints—and call out where cosmetic visibility matters. Use tabs and slots to self‑locate, reduce the need for heavy tack; and when you do tack, remember a tack weld is a temporary welding technique and must be dressed where visible.
Note on positions: Record whether fillets are done in 2F weld or other positions; consistent position improves appearance.
RFQ Snippets You Can Paste
Visible faces: Class B, match grain, treat discoloration; stainless to ASTM A967; inspect at 800 lux.
Sanitary zones: Class A, Ra ≤ 0.8 µm (≈ 32 microinch finish); document measurement site and stylus cutoff.
Hidden frames: Class C, remove spatter, break edges; prep for coating; no undercut per ISO 5817‑B unless otherwise stated.
Coating: pre‑treat to supplier spec; verify adhesion on welds; avoid arc mark welding scars on visible panels.
Table — Example phrases buyers use
| Intent | Buyer wording that works |
|---|---|
| Polished stainless fascia | “Class A on fascia; 40 surface finish target; passivate per ASTM A967; electropolish optional; inspect 800–1000 lux.” |
| Powder‑coated frame | “Class C on internals; Class B on exposed frame; bead blast surface finish prior to coat; no telegraphing; edge radius ≥ 0.5 mm.” |
| Mixed visibility enclosure | “Map zones: A front, B sides, C interior. Record weld position; avoid back step welding marks where visible.” |
Inspection That Prevents Surprises (And Arguments)
Agree on how finish will be verified before the first article. Use an AQL plan (for example, AQL 1.0 on critical, AQL 2.5 on majors) and define inspection light level. For roughness, document instrument, cutoff, and location. For stainless, require a water‑break‑free test after cleaning and passivation. Photograph visual standards—Class A/B/C exemplars—under the agreed lux.
Tie finish to function: porosity that breaks through after light grind is a red flag. Note common causes of weld porosity (contamination, shielding loss, improper parameters) and reject lots where porosity becomes visible after cosmetic dressing. Agree that cracking welding evidence is cause for immediate hold. If you allow soldering versus welding on small features, record where each is acceptable; typical export programs keep structural joints to welding and reserve solder or solder weld only for non‑structural attachments.
Where your drawings state 32–125 surface finish bands, sample each zone. If the program calls for 125 machine finish on concealed brackets, do not over‑engineer and then charge the supplier for needless polish; consistency beats sparkle where no one looks.
What Process Mix Works at Scale (Without Over‑Paying)
For sheet work, the best welding for sheet metal often blends TIG for visible corners with MIG for throughput on hidden frames. Document the split so quotes are comparable. When discussing manufacturing welding budgets, include time for spatter removal, edge break, and cleaning; those minutes are where Class B becomes profitable. If a supplier offers contract welding & fabricating, request takt‑time data and sample photos at your target lux level.
On robot‑ready parts, the benefits of robotic welding include lower variation, cleaner beads, and predictable finishing time. Robots also reduce stray strikes that show up as arc mark welding scars on show faces. For aluminum housings, decide early whether the visual is aluminum surface finish with brush, or full color powder; the two require different prep.
Compact Decision Matrix (Start Here in a Kickoff Call)
| Use case | Visibility | Environment | Material | Class | Roughness | Post‑weld | Notes |
| Commercial kitchen fascia | High | Chlorides, heat | 316 | A | 32 µin | Pickle/passivate, electropolish optional | Brush direction documented |
| Retail frame, indoor | Medium | Low | Carbon steel | B | 40–63 µin | Bead blast + powder | Edge radius ≥ 0.5 mm |
| Internal machine base | Low | Industrial | Carbon steel | C | 125 µin | Prep + powder | Focus on straightness |
| Anodized housing | High | Indoor | Aluminum | A/B | 40–63 µin | Brush + anodize | Discuss color at seams |
| Decorative brass rail | High | Indoor | Brass | A | 40–63 µin | Polish + seal | Prefer brazing to reduce halos |
Buyer‑Focused FAQ
What finish should I call for on food‑service stainless? Class A on touch zones, Class B on adjacent faces, Class C inside. Target 32 microinch finish on product contact and require passivation per ASTM A967. Document how Ra is measured.
Can Class C with powder survive outdoor retail? Yes—if prep is right. Use bead blast or equivalent profile, seal corners, and design drainage. Many buyers reserve Class B on the show frame and Class C internally.
Will polishing weaken a joint? Only if you remove too much. Design for welding by leaving material to blend. Keep heat down while finishing.
Welding versus soldering—when to use which? Structural joints stay welded. Small non‑structural attachments can be brazed or soldered when appropriate; write the allowance into the RFQ.
Do I need to worry about positions and joint types? Yes. Record weld positions (e.g., 2F weld on fillets) and remember the 5 basic weld joints when dimensioning. Clarity here equals predictable finish.
What about alloy steels? For industrial frames with AISI 4130 welding, specify preheat and cooling window. Clarify whether PWHT is required and keep finish to Class C unless faces are exposed.
Quality, Packaging, and Transit
Finish can be damaged in the box. Require protection on show faces, desiccants for stainless after passivation, and separators that do not imprint brush grain. State that inspection is at pack‑out light level with random opens per your AQL. Add a simple rule: if a part fails the visual standard at unbox, the shipper replaces packaging method before next lot.
Conclusion
A clear welding finish strategy turns drawings into reliable products. Tie class to visibility, set roughness by zone, and name the post‑weld path. Specify how you will measure success—lux level, Ra method, AQL—and you will avoid disputes, cut rework, and get predictable quality at scale. This is how overseas programs stay on time, on spec, and on budget.
Share your next RFQ draft with finish zones, roughness bands, and post‑weld steps annotated. One early review prevents many late emails—and keeps your launch on schedule.