Milk and aluminum

[PaulLag]

Hi there

hope everybody is fine
Please, I'd like to ask you as follows

I have had an inspection of a cold room where there is fresh milk.
Into the room there is a cooler with aluminum fins thant has been corroded.

My question is:
I kow that in cold rooms where there are diary product stainless steel is recommended.
I can't find any literature reference concerning aluminum and milk.

My point is: can aluminum be utilized with milk ?

Many thanks

 

[CoryPad]

Can you provide information about the aluminium fins? Alloy, heat treatment, surface coatings, etc.?

Bovine milk usually has a pH of 6.7, which usually is not a problem for aluminium.

 

[PaulLag]

Hi many thanks for your answer.

Aluminum is a series 7000 fin.
No surface coating
thanks

 

[bimr]

I don't believe that milk is corrosive, but lactic acid can develop.

Lactic acid develops in cow’s milk as a result of bacteria fermenting (breaking down) the lactose. Freshly expressed milk does not contain lactic acid. It is only after a short period of time that the concentration builds up due to the input of bacteria. This means that lactic acid can be used to assess the quality of milk and its state of preservation.

Here are some corrosion charts:

http://www.smt.sandvik.com/en/materials-center/corrosion-tables/milk/

http://www.smt.sandvik.com/en/materials-center/corrosion-tables/lactic-acid/

http://www.americanconduit.com/wp-content/uploads/2012/08/RAC-Binder_Chemical.pdf

Guess that is why most of the equipment in milk plants is fabricated from stainless.

 

[EdStainless]

I would be more concerned about the chemicals used to clean and sterilize the equipment. That is most likely what has attacked the Al.

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P.E. Metallurgy, Plymouth Tube

 

[DeleteriousPhases]

any pictures of the fins?

 

[ornerynorsk]

7xxx series aluminum is not recognized as an approved food equipment material. See ANSI/NSF 51-1997.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[bimr]

The OP says the fins are in a cooler, not part of food processing equipment. Would think that the cooler is infrequently cleaned as well.

 

[ornerynorsk]

ANSI/NSF 51-1997 describes incidental possibility of contact as well as direct contact for any equipment within the food zone.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[Sloss]

I would think that the fins are on the external surface of the cooler and will never come into contact with the milk unless there is a spill or failure resulting in a clean down to the drains. The product would not be returned to the system.

Possibly a Galvanic corrosion depending on the material of the actual cooler?

 

[bimr]

Agree that ANSI/NSF 51-1997 does not prohibit the use of aluminum in splash zones or nonfood zones.

However, there is a general statement in Section 6 regarding corrosion that should effectively prohibit aluminum fins for this application:

"Materials shall be corrosion resistant in the intended end use environment."

 

[EdStainless]

Prob standard cooler design with either Al or Cu tube and Al fins.
My money is on them splashing it with sanitation chemicals (low pH and/or high Cl).

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P.E. Metallurgy, Plymouth Tube

 

[CoryPad]

Ed,

I think the sanitation chemicals is a good theory. But, aluminium is usually more sensitive to high pH conditions. So, how about sodium hypochlorite, which is a common sanitation chemical and is basic?