Each material differs.
Right finish per material.
Material-tuned.
Different materials accept different finishes. Aluminum anodizes; steel doesn't. Brass polishes well; titanium colors via interference.
Key principles.
Anodize, paint
Type II decorative or Type III hardcoat. Wet paint or powder coat.
Plating, paint
Zinc plating, hot-dip galvanizing, painted or powder coat.
Polish, passivate
Mechanical polishing, electropolishing, passivation.
Polish, lacquer
Mechanical polishing. Clear lacquer prevents oxidation.
Polish, patina
Polishing or controlled patina (browning) for aesthetic.
Anodize (interference)
Voltage-controlled anodize creates interference colors.
Paint, polish
Paint with adhesion primer. Polish for clarity.
Specialty
Conversion coating, painting. Reactive material.
Glazing, polish
Ceramic glaze for color. Polish for transparency.
FAQ
Anodize all metals?
No. Anodize works for aluminum (Type II/III), titanium (interference colors), niobium. Not stainless or steel.
Paint adhesion?
Steel: easy with primer. Aluminum: needs alodine pretreatment. Stainless: difficult, needs etch primer. Plastic: per material primer.
Stainless passivation?
Citric or nitric acid removes free iron from machined surface. Restores corrosion resistance after machining.
Brass tarnishing?
Brass naturally darkens (oxidation). Lacquer coat preserves bright finish. Or accept patina.
Copper finishing?
Polish for bright copper. Patina for aged appearance. Lacquer coat preserves either.
Multi-material assemblies?
Different finishes per material. Anodize aluminum, plate steel, polish brass. Integrate per design.