Compare exposure at the component

An underside, recess or rain shadow may collect airborne contamination but receive little washing. An open face may be wetted more often yet lose some deposits through runoff. ASSDA identifies sheltered and poorly drained stainless surfaces as relevant exposure conditions. This supports a local comparison; it does not establish that every sheltered turbine surface will corrode faster or that a particular finish is suitable for marine service.

Look for paired observations

Compare the same material and finish where possible, because a different alloy or coating makes the comparison ambiguous. Useful evidence includes deposit boundaries, repeated damp patches, orientation and the points where water accumulates. If sheltered and open parts differ in temperature or runoff from another component, note that difference too. A clean surface above a corroded pocket cannot be used as a control unless those exposure differences are understood.

If two sides use different coatings, they cannot isolate the effect of shelter without accounting for that difference. A paired comparison becomes stronger when the material system is the same and the principal known difference is local washing, retention or drying.

Choose a targeted protection review

Ask whether the affected geometry has a local cleaning, drainage or protection requirement in the applicable instructions. Do not add holes, remove covers or alter sealing in response to the general mechanism. If the sheltered region is inaccessible, its condition may require a planned qualified examination. The practical result should be a component-specific exposure response, rather than a whole-site corrosion classification inferred from one patch.