Dear Dr. Atik Islam ,

not knowing the type of aluminum, its location in the system, the fluids involved and other chemical-physical parameters that characterize the system, I would say that answering your question is quite difficult.

Personally ... and I seem to have already given you this answer ... I would say that the thing that intrigues me the most is where the localized corrosion (internal or external of the pipe) starts from, just to be sure.

As the conformation of localized pitting corrosion is generally V-shaped, with the largest area where it began, a cross-sectional analysis of the pipe , in the area of the hole, would be my first step ...

Then, of course, I would delve into further analysis.

My best regards, Pierluigi Traverso.

https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/4580/ESL-HH-02-05-30.pdf?sequence=5.

https://www.duffnerengineering.com/aluminum-tube-corrosion/

Pierluigi Traverso Thank you sir,

Previously, you given the answer of the same question , but I am not cleared about this question.

Now I am telling this tube In detail with Picture.

The grade of the tube is 1060

This tube work as a refrigerator evaporator

Dear Dr. Atik Islam ,

I suggest you to have a look at the similar RG question, where your colleague, here on RG, had a similar problem:

-Could you please inform me that how long at least I should perform the SALT SPRAY TEST on Aluminum evaporator tube to get so?

Available at: https://www.researchgate.net/post/Could-you-please-inform-me-that-how-long-at-least-I-should-perform-the-SALT-SPRAY-TEST-on-Aluminum-evaporator-tube-to-get-so

Generally speaking, aluminum alloys form a protective passivation layer which, however, can be easily attacked and give rise to localized corrosion phenomena in the presence of Cl- ions, further accentuated by crevice and / or galvanic corrosion phenomena.

The passivation layer that forms can be made more protective by using corrosion inhibitors suitable for the environment with which the product is in contact.

My best regards, Pierluigi Traverso.

Dear Dr. Atik Islam

I assume the pipe is of 3xxx or 1XXX Aluminum, and also that It qualifies the minimum required Corrosion testing (SWAAT / CASS) hours.

Although the given information is insufficient to conclude, I see two possible reasons :

1. As visible in one picture, it is joined with Copper pipe, at a distance from the leak, right?

To avoid galvanic corrosion, you might have insulated the joint area, right?

If you use a thin insulating layer, then during operation water may condenser over it because of low Temperatures there. If the insulating material itself gets covered with water/mist, then you may still see galvanic corrosion where the insulating sleeve ends on Aluminum Side. It completes the circuit for ions exchange. The length of the insulating sleeve is also important.

2. If that's not the case, is there any clamping there, which may create a crevice?

Please confirm my assumptions, and also let me know the environment under which it is operating.

Jagdeep Singh Thank you sir

Pure aluminum tube 1xxx use for refrigerent evaporator tube. Coor air flow through the refrigerator. Below I given the picture of the the Aluminum tube. The inner side of the tube also be given . The probability cause of pitting corrosion also to be given.

1. The rotten blood of the meet or fish water probable to be enter into the tube.

2.Presence of inclusion Particles

3.Heterogeneti of thickness

4. Effect of compressor oil

5.Effect of condense air on aluminum tube. etc

My Question is why this type of localized corrosion occur

Jagdeep Singh Dear Sir

Below I given some more field aluminum tube picture.

Dear Dr. Atik Islam ,

my apologies if I am repetitive but knowing on which side of the pipe the pitting begins is a simple procedure and from this it is possible to make more realistic considerations. The description would be more complete if one knew exactly what flows inside the tube and what the external environment may be in contact with the corroding tube. Reading your e-mail and knowing different types of refrigeration systems and seeing the photo you have shown, I made the following hypotheses, which may not be true but should be verified by you. -It seems very strange to me that the rotten blood of the meet or fish water probable to be enter into the tube, generally in the tube (inner zone) should flow a fluid capable of exchanging heat, pure and free of particles and impurities.

Given the positioning, in contact with an insulating system of solidified polymeric "foam" type it is possible that condensation water and the presence of areas of crevice and impurities (especially containing chlorides) may have triggered this localized corrosive phenomenon.

However, it is necessary to carry out morphological and chemical analyzes to verify any possible supposition.

My best regards, Pierluigi Traverso.

Atik Islam

What I understand is the Aluminum pipe is carrying a low-temperature refrigerant inside it for producing a refrigeration effect. I see, Aluminum pipe is covered with tape most of the places, is that right? The location where the leak happened, was it bare/uncovered?

My opinion on the points you said.

1. The rotten blood of the meat or fish water probable to be entered into the tube.

>That's not the cause of corrosion/leak. The refrigeration circuit is sealed. If you found such traces in the refrigeration circuit, those must have been sucked after the leak because of lower-than atmospheric pressure inside the pipes (although it is not preferred for the same reason).

2. Presence of inclusion Particles

>The filter is always there in the circuit. Even if it's not, it can never localize wear to cause a leak.

3. Heterogeneti of thickness

>Do you mean tube puncture due to high stress at a low thickness region?

I don't think so, but you can confirm it by checking the failed sample.

4. Effect of compressor oil

>NO

5. Effect of condensed air on aluminum tube. etc

>Yes, that's highly probable. Water gets condenser over the tubes and freezing there probably. Especially in coastal areas, it's not only the water but also salts that can get accumulated there.

I don't think corrosion kinetics are great enough to induce corrosion at refrigeration temperatures. You may need to investigate the usage history of the product. Like if you don't use the refrigerator for any reason (like breakdown, maintenance, no usage, seasonality, etc), ice will melt leaving behind salts and humid air which is sufficient to cause corrosion over a period of time.

Now, why only localized corrosion happened, remains a question.

Please check, was the leakage area the only area which was not covered with tape? Any possibility of water being preferentially accumulated there? Any crevice formation there, I think so, because of pipe being packed in that foam.

Also, you have to check what thickness of pipe you have taken? Corrosion will only cause pitting to some depth increasing the stress concentration, failure in the form of a puncture is very likely to happen due to high stresses, especially when equipment is not working because working pressures are much lower on the evaporator side.