Three surface finishes are common for stainless appearance parts:

1) Brushed (No.4 / hairline): unidirectional grinding with abrasive belts or flap wheels. Acceptance checks grain straightness, uniformity, colour consistency and direction; keep the same direction within a batch. 2) Mirror (No.8): multi-stage polishing to roughly Ra ≤0.1 μm depending on requirements. Acceptance checks reflection clarity, absence of scratches and polishing compound residue; mirror surfaces show fingerprints and scratches, so protective film is needed. 3) Blasted (sand/bead blasting): uniform matte surface. Acceptance checks roughness (Ra), uniformity and colour difference; blasting changes the passive state, so post-blasting passivation is usually required.

Guidance:

• Specify the finish code and an approved sample to avoid “close enough” disputes. • Agree the brushing direction in the order. • Protect mirror surfaces with film during transport. • After brushing/blasting, passivate and run a blue-dot test where corrosion resistance matters.

Surface finish affects appearance, corrosion resistance and cleanability — write the acceptance criteria into the technical agreement.