Is it possible that this component has been heavily weathered, possibly in contact with some form of alkali, e.g. NaOH? This looks like it could be smut. May be worth considering, if so, then desmutting processes are avaliable.

Edward Wright

Thank you sir for reply me.

This is refrigerator tube. This tube remain inside the foam.

Dear Sir, Edward Wright

Below I given a Aluminum tube .

Here Look Sir, this tube remain inside the foam of a refrigerator.

This tube leakage occur, Can you give me the root cause of this type of leakage & how can I prevent it.

Dear Atik,

It is quite unusual, do you happen to know the composition of the foam, is the evaporator in a sulphur rich air environment?

You say that the tube is leaking the working fluid?

It would be quite straightforward to take a very small deposit sample of the black stuff, and conduct a chemical analysis to gauge an idea of what it may be.

Best wishes,

Edward