Process
Plating and coating
Finish is a sequence, not a color chip. On 4–14 mm wire we form and weld, then rack-plate and/or run in-line powder — or we buy pre-coated wire and live with what the bend does to it.
What finish actually is
A wire form leaves the bender as mill steel, stainless, or whatever was on the coil. Corrosion and appearance come after — or they were already on the wire. Mixing those two paths on one line item is how you get a cracked zinc radius and a surprised PPAP.
We run rack plating and in-line powder on the formed part. Exotic specs still go out. The process rules do not change: name the spec, the thickness, and whether powder sits on plate or on pretreated mill.
Pre-coated wire vs post-form finish
Pre-galvanized / pre-painted wire — cheaper at volume, ugly at a tight inside radius. The coating stretches on the outside fiber and can flake. Straightener marks show. Welds burn it off locally; you will see a halo unless you dress and touch up.
Form then finish — the honest path for most 4–14 mm frames, wire baskets, and anything that is welded. Plate or powder sees the finished geometry. Weld flash has to be called: as-welded under plate, or dressed.
Stainless is usually passivate, not paint. Powder over mill steel needs a pretreatment that matches the spec, not “black paint.”
Rack plating — zinc family
3/8, 7/16, and 1/2 in forms hang on a rack. Barrel plating is for small loose parts; a 12 mm frame does not belong in a barrel. We run the zinc family that industrial wire actually specs:
- Zinc — alkaline for even coverage on a bent form; acid chloride when the print wants a brighter deposit. Call ASTM (or equivalent), microns, and chromate. Acid zinc on high-tensile wire needs a hydrogen bake.
- Zinc-nickel — higher corrosion life than straight zinc. The usual upgrade when the part lives outside, on a vehicle, or in a plant that used to fail salt spray on zinc alone.
- Zinc-iron — alloy zinc when the spec wants it instead of Zn-Ni. Same rule: thickness and chromate on the print, not “silver plate.”
- Nickel — appearance and wear. Thickness matters on a fit diameter.
Racks, thieves, and current density decide whether the inside of a tight 3D loop plates or starves. A sample racked the way production will rack is part of first article — not an afterthought.
In-line powder coating
In-line means a conveyor: hang, wash / pretreat, dry, spray, cure. Not a batch booth for every job. Stock 3/8, 7/16, and 1/2 in frames, hangers, grids, and baskets hang on line hooks and run. Color, gloss, and max film build belong on the quote.
Powder build eats a tight clip gap and a threaded end. Call max thickness on mating faces. Batch powder stays available when the form will not hang consistently or the lot is too small to set the line.
Pretreat is the process. Powder on dirty mill or on an unmatched conversion coat peels. We do not skip wash to “save a pass.”
Plate, then powder
Corrosion plus a color is a dual coat: rack zinc, zinc-nickel, or zinc-iron, then in-line powder over the plate. That is one sequence in this shop — not plate here and powder three states away. The print has to name both layers. Powder over chromate is not the same as powder over phosphate; say which.
Passivate stays the stainless path. Do not powder 304 to “make it look finished” unless the print wants a color, not corrosion.
What changes from 4 to 14 mm
| Diameter | Inch | Finish |
|---|---|---|
| 4 mm | 0.157 in | Pre-galv is common and will crack on a 1× bend. Powder build is a large fraction of diameter. Barrel plating may still apply. |
| 8 mm | 0.315 in | Form-then-zinc is the usual frame path. Rack. In-line powder hangs clean. |
| 12 mm | 0.472 in | Rack plating. Weld then plate. Pre-coat is a last resort. Dual coat is routine on outdoor frames. |
| 14 mm | 0.551 in | Finish is secondary to the structure. Spec thickness on faces that mate, not ‘cover all over.’ Rack and hang with real hooks. |
What to spec
- Plating: zinc, zinc-nickel, or zinc-iron — spec, microns, chromate
- Powder: color, gloss, max film on mating features
- Dual coat: plate then powder, and which pretreat sits between
- Before or after weld; before or after end forming
- Hydrogen bake if the wire is high-tensile and the plate is acid
- Surfaces that must stay bare (threads, weld later, ground datums)