Flat-fan nozzles are the default for anything requiring edge-to-edge uniformity on a flat strip — rust preventives, galvanizing passivation, and rolling mill lubrication all use this pattern because it's straightforward to array across a width and overlap correctly. Full-cone nozzles suit phosphate and conversion coating arrays and other applications needing volumetric coverage rather than a linear sheet. Air-atomizing nozzles are used where droplet size control matters more than raw coverage — coil coating primers and paints, and ultra-fine anti-fingerprint top coats, both need the finer, more controllable droplet spectrum that compressed-air atomization provides.

Uniformity comes from three things working together: correct nozzle spacing and spray angle so adjacent spray zones overlap consistently, flow rate matched precisely across every nozzle position in the header, and — on lines running variable speed — flow control linked to a line-speed sensor so coating weight in g/m² stays constant even as throughput changes. Edge buildup or centerline starvation are the two classic failure symptoms, and both usually trace back to incorrect overlap calculation or a header with position-to-position flow variation rather than a fundamentally wrong nozzle choice.

Phosphate conversion lines run acidic phosphating solutions (pH 2–4) and often alkaline cleaning stages (pH 9–13) in the same system, so nozzle wetted materials need to handle both ends of that range. 316 stainless steel is adequate for many phosphate chemistries; PTFE, PVDF, or Hastelloy are specified where the specific acid concentration, temperature, or chromate chemistry would otherwise attack standard stainless. Seal compounds need the same scrutiny — a body material rated for the chemistry doesn't help if the seal degrades and creates a leak path first.

Higher line speed means less residence time under the spray header for a given coating weight target, which generally requires either higher flow rate or additional spray zones to deposit the same film in less time. On lines that run a range of speeds — commonly 30–250 m/min in steel processing — flow control needs to be linked to actual line speed so coating weight in g/m² holds constant rather than dropping off as speed increases. A system tuned only for one speed point will under- or over-coat whenever the mill runs somewhere else on that range.

Yes, substantially. Flood coating or oversized nozzles apply far more coating material than the target film weight requires, with the excess running off or requiring recovery and disposal. Precision spray systems sized to the actual required coat weight, with correctly calculated overlap and droplet size matched to the coating's transfer efficiency, typically cut chemical consumption 40–60% compared to flood coating or excess spray application — while also reducing the volume of waste treatment and improving environmental compliance margins.

Streaking and bare spots almost always trace back to either spray pattern overlap or droplet size mismatch. Insufficient overlap between adjacent nozzles leaves gaps at the pattern edges that show up as streaks running in the line direction. Droplet size that's too coarse for the coating's surface tension can produce uneven wetting rather than a continuous film, particularly on textured or oily substrates. Clogged or worn orifices distort the pattern from one nozzle without necessarily reducing total header flow, so the defect can appear localized to one lane across the strip rather than uniformly across the width — checking individual nozzle patterns, not just total flow, is the first diagnostic step.