How to distinguish whether the stainless steel underwater lamp is rusty or dirty?

When consumer buying the stainless steel underwater lamp,they say it’s easy to rust even it’s 316L stainless steel,but what make us embrassing is sometime they send back the rusty underwater lamp,but we find it’s just dirty.
how to distinguish whether the stainless steel underwater lamp is rusty or dirty ?

1. Look at color of the underwater lamp
Rust: Usually reddish brown or orange.
Dirt: A variety of colors, may be black, gray or other colors, depending on the contaminant.

2. Touch the surface of the underwater lamp
Rust: The surface may be rough or even convex or peeling.
Dirt: The surface is usually smooth and dirt can be wiped off with your fingers.
3. Test the underwater lamp with detergent
Rust: After wiping with a mild cleaner (such as soapy water), the rust will not disappear.
Dirt: Cleaners are usually effective at removing dirt.
4. Test the underwater lamp with an acidic solution
Rust: Wipe with white vinegar or lemon juice, rust will be reduced.
Dirt: The acid solution has no obvious effect on dirt.
5. Check the environment of the underwater lamp
Rust: More likely to occur in wet or salty environments.
Dirt: More common in dusty or oily environments.
6. Use sandpaper or steel wool to test the underwater lamp
Rust: After gentle sanding, rust will be reduced, but may leave marks.
Dirt: The dirt will be removed and the surface will return to shine.

stainless steel 316L underwater lamp for your reference :

To make a brief conclusion:
Rust: reddish-brown, rough, not easy to remove, acid solution effective.
Dirt: colorful, smooth, easy to remove, cleaning agent is effective.
Now you know how to distinguish whether the stainless steel underwater lamp is rusty or dirty ? welcome to leave us your feedbacks~