From Raw Steel to Showroom Finish
A great clothesline isn't just about clever design — it has to survive the New Zealand outdoors for years. That means UV, salt air, rain, and all the abuse a backyard can throw at it. The colour finish on every Swift Dry product is powder coating, but the real story starts much earlier, in the pre-treatment stages that make the colour stick and last. Here's a look behind the scenes at the full journey — from raw galvanized tube to finished, packed product ready to ship.
01 — Initial Cleaning & Degreasing
Galvanized steel tube arrives from the supplier coated in mill oils, grease, handling residue, and storage contaminants. Before anything else, every piece goes through a thorough degreasing stage — typically using an alkaline cleaner or a solvent wash — to strip away all surface oils. This matters enormously: any grease left behind will prevent subsequent treatments from bonding properly and create fish-eye defects in the final coating. Tubes are either spray-washed or dipped in a heated degreasing bath, then rinsed clean with fresh water.
Why it matters: The colour finish is only as good as the surface beneath it. A contaminated surface will cause adhesion failure and peeling within months.
02 — Acid Wash (Etching)
Once the tubes are clean of grease, they go through an acid wash — also called etching or pickling. A diluted acid solution is applied to strip the zinc oxide layer from the galvanized surface and remove any light surface rust. This process slightly roughens the metal at a microscopic level, creating a textured profile that gives the powder coating a much stronger mechanical key to grip onto. After etching, the tubes are rinsed thoroughly to remove all acid residue and neutralised.
Good to know: Skipping the acid etch on galvanized steel — a notoriously difficult surface to coat — is one of the most common causes of premature powder coating failure.
03 — Phosphate Conversion Coating
After the acid etch and rinse, parts go through a phosphate conversion coating stage. This chemical treatment reacts with the bare metal surface to form a thin crystalline phosphate layer that serves two roles: it significantly improves adhesion for the powder coat, and it adds a first line of corrosion protection beneath the coating. Parts are then given a final demineralised water rinse to ensure no contaminants remain before the oven.
04 — Racking, Drying & Pre-Heat
Once washed and rinsed, parts are hung on a conveyor rack using wire hooks — this is called racking. Every piece needs to hang freely so all surfaces are exposed and the earth connection is made cleanly, which is essential for the electrostatic powder application that comes next. Wet parts cannot go into the powder booth — moisture causes powder to clump and adhesion to fail — so racked components first pass through a dry-off oven at around 120–150°C to evaporate all surface moisture.
05 — Powder Coating (The Colour)
Now the colour goes on. Dry powder — a fine mixture of resin, pigment, and flow agents — is loaded into an electrostatic spray gun. The gun imparts a negative electrical charge to the powder particles as they leave the nozzle, while the metal component is earthed (grounded). This electrostatic attraction pulls the powder firmly and evenly onto the part, including into recesses and around curved tube profiles. The result is a uniform, dry coating that clings in place before it is ever cured. Racking positions are carefully chosen so that all surfaces receive even coverage with no shadow areas.
Key detail: Electrostatic application means far less waste than liquid paint — overspray powder is collected and reused.
06 — Curing in the Oven
Coated parts are moved carefully into the curing oven. At temperatures typically between 180°C and 200°C, the powder undergoes a chemical transformation: the resin melts, flows into a smooth continuous film, then cross-links into a hard, durable thermoset polymer. Cure time is usually 15–25 minutes at temperature. The result is a coating significantly harder and more impact-resistant than liquid paint, with excellent chemical and UV resistance. Under-curing leaves a soft, chalky finish; over-curing can cause colour shift or embrittlement — so oven calibration and timing are critical.
07 — Quality Inspection
Once cooled, every batch is inspected under good lighting for surface defects: runs, pinholes, thin spots, contamination specks, or colour inconsistency. A dry-film thickness gauge is used to verify the coating has reached the correct thickness — typically 60–80 microns for outdoor products. Any part that doesn't pass is stripped and recoated rather than shipped.
08 — Packing: To the Coater & Back
Packing is a two-way story. Before parts leave our factory for the powder coater, they need to arrive in perfect condition — any dent or scratch on a raw part means a visible flaw in the finished colour. And once they come back with a powder coat on them, the stakes are even higher.
Raw fabricated parts are layered flat on timber pallets with plastic film between layers to prevent metal-on-metal contact. The whole pallet is stretch-wrapped firmly to lock everything in place for the journey. When the coated parts arrive back, tubes are sorted, sleeved in foam tubing at any contact points, and re-palletised with foam or bubble wrap separating every layer. Cardboard end protection goes on before the final stretch wrap.
Our rule: If it can rattle, it can scratch. Every piece should arrive looking exactly as it left the oven.
09 — Assembled, Boxed & Out the Door
Once all components have passed inspection, the final stage is assembly packing and dispatch. Hardware, fittings, and instructions are packed alongside the powder coated components into Swift Dry retail cartons — white boxes for hardware packs, and the distinctive purple and green Skyline branded boxes for our flagship clothesline range. Orders are palletised, labelled, and stretch-wrapped for courier or freight delivery anywhere in New Zealand.
What started as a bundle of raw galvanized tube is now a finished product, ready to be unboxed and installed in someone's backyard. From acid wash to retail shelf, every step has been deliberate.
Built to Last — From the Inside Out
Powder coating done right is one of the most durable surface finishes available for outdoor steel products. But it lives or dies on preparation. The cleaning, acid etch, and phosphate stages are unglamorous and time-consuming — but they're what stands between a coating that lasts a decade and one that peels within a season. At Swift Dry, every clothesline goes through this full process before it reaches your backyard. That's the standard we hold ourselves to, and it's why our products are built to handle whatever New Zealand weather has in mind.
