Check the pattern and source

Staining below a carbon-steel attachment may be transferred corrosion product. Fine discoloration on a salt-retaining surface can have another origin. A concentrated mark at a crevice deserves a different question from a broad film on an open face. ASSDA distinguishes tea staining from other staining causes. That distinction supports investigating alternatives, not classifying an unknown wind component as cosmetic from its brown colour alone.

Look beyond colour

The next evidence concerns surface continuity: whether there are discrete pits, a roughened area, an opening at a joint or staining that reappears from beneath a cover. Inspection access and any permitted cleaning need to be arranged by the responsible service team. An alloy designation, surface finish and chemical exposure history can be more useful than a closer unscaled image. Do not assume the word stainless means every alloy resists every environment.

If the stain is removed under an approved method and discrete cavities remain, the question has changed from colour to localized material condition. The reviewer should address those cavities explicitly rather than carry forward an earlier appearance-only classification without reconsideration.

Select the appropriate response

Ask the materials reviewer whether the observation fits superficial staining, external contamination or a localized attack needing measurement. Keep any cleaning proposal separate from acceptance of the remaining part. A cleaner that removes colour may alter evidence or be incompatible with adjacent seals and coatings. MARSTON stainless grades and component protection are unconfirmed here; the outcome must be based on the actual supplied material and the affected function.