Paint, powder, plating and anodising all buy their service life before they are applied. Every Australian surface-preparation standard says the same thing on page one: before the profile, before the primer, before anything mechanical — get the surface clean. This guide maps the standards and shows where cleaning fits.
Classic UK trials from the 1950s showed that blast cleaning more than doubled the life of oil-based paint on steel — surface preparation is the single biggest lever on coating life, bigger than the choice of paint itself. But a visually perfect blast is not enough. Coating systems fail early on surfaces that look clean and are not:
| Job | What it means | What happens if you skip it |
|---|---|---|
| Remove visible contamination | Rust, mill scale, old coatings, dirt | Coating bonds to scale, not steel — sheet delamination as the scale lets go |
| Remove invisible contamination | Oils, greases, drawing compounds, weld smoke, soluble salts, fingerprints | Fisheyes and pinholes at spray time; osmotic blistering and creeping adhesion loss in service |
| Create the right profile | Anchor pattern matched to the coating system's specified range | Too smooth: poor mechanical key. Too deep: peaks stand proud of the film and rust-spot |
The AS 1627 series covers metal surface preparation for protective coating. The parts most relevant to manufactured parts and steelwork:
| Standard | Covers |
|---|---|
| AS 1627.0 | Selecting the right preparation method for the job |
| AS 1627.1 | Removal of oil, grease and related contamination — solvent and alkaline cleaning. The first step, always |
| AS 1627.2 | Power-tool cleaning |
| AS 1627.4 | Abrasive blast cleaning |
| AS 1627.5 | Pickling — acid removal of scale and oxide |
| AS 1627.6 | Chemical conversion treatment — phosphate and similar pre-coats |
| AS 1627.9 | Pictorial surface preparation standards (aligned with ISO 8501-1) |
Blast and tool cleanliness is graded to ISO 8501-1: Sa 1 (light blast) through Sa 2, Sa 2½ (near-white — the workhorse grade for high-performance systems) to Sa 3 (white metal), and St 2/St 3 for hand and power-tool preparation. Coating data sheets specify the grade they need — and every one of those grades assumes the degrease has already happened.
Solvent wiping — the rag-and-thinners method most workshops call degreasing — redistributes contamination as reliably as it removes it: the last wipe leaves a thin, even film of everything the rag has touched. Immersion cleaning removes contamination to the drain instead of spreading it, reaches every hole, fold and internal passage, and leaves nothing behind but rinse water.
The water-break test costs nothing and does not lie. It is the difference between "looks clean" and "is clean" — and it is the acceptance test we recommend building into any pre-coat process step, because it catches the invisible contamination that causes the expensive failures.
| Finish | What the surface must be |
|---|---|
| Liquid paint | Degreased, profiled to the system spec, dry — primer windows are time-limited once prep is done |
| Powder coat | Degreased and usually conversion-coated (AS 1627.6) — powder magnifies surface defects rather than filling them |
| E-coat | Immersion-grade cleanliness — the process is a bath, so the prep must be bath-uniform too |
| Electroplating | The least tolerant of all — plating amplifies any residue as a visible defect and adhesion failure |
| Anodising | Chemically clean aluminium — oils shadow the anodic film and dye take-up |
For structural steelwork on site, AS 1627.1 means solvent or alkaline washing before blasting. For manufactured parts — fabrications, pressings, machined components, die castings — the same step is done better in a tank: heated alkaline chemistry, ultrasonic agitation into every feature the spray gun will later reach, a clean rinse and a hot-air dry. The result is a water-break-free surface produced by recorded parameters — chemistry, concentration, temperature, time — so batch four hundred is prepped identically to batch one, shift after shift.
When a coating fails early, the investigation almost always ends at the substrate: a drawing compound nobody removed, a solvent wipe that smeared instead of cleaned, a blast over an oily surface. Fix the preparation step and the "paint problem" disappears.
Related reading: Metal finishing & surface prep · Spray, coating & atomisation · What temperature should the bath run at? · Cleaning chemistry. Ready to test it on your parts? Book a cleaning trial and bring the water-break test with you.
AS 1627 series — Metal finishing — Preparation and pretreatment of surfaces (Parts 0, 1, 2, 4, 5, 6, 9; current parts reconfirmed 2017).
ISO 8501-1 — Preparation grades Sa 1 to Sa 3, St 2 and St 3 (adopted in AS 1627.9).
SSPC-SP 1 — Solvent Cleaning, the precursor step to all mechanical preparation.
Australasian Corrosion Association / corrosion.com.au — steel surface preparation standards overview, including the 1950s UK coating-life trials.