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topic 18415

Aluminum Heat Exchanger


2002

A specialty type of the heat exchanger, extruded from the aluminum alloy, has developed within its inside channels deep groves. The understanding is that the groves are the result of combination of corrosion, chemical and oxidation, and erosion caused by flowing water. It looks that the erosion takes over once the corrosion makes initial progress braking the otherwise smooth surface. Can the heat exchanger be sand-blasted internally, or cleaned in some other way, and coated to prevent further progress of the erosion/corrosion?

Stan Blovish
- Toronto, Ontario, Canada


2002

Dear Stan,

Yes you can do it by chemical conversion named alkaline chromating. Our company did it for air type heat exchanger of power plant.it is an old processes but the time anodizing is impossible it is a substitution. It protect inside and outside of heat exchanger . To start look for MBV processes.

Hadi Khosarvi
- Tehran, Iran


2003

Dear Hadi,

We greatly appreciate your advice. Stan is away and I will continue the project to its final completion. Can the MBV method be applied at the site, without dismounting the heat exchanger and moving it to a factory? The heat exchanger is constructed with over 100 aluminum extrusions, which are cooled with water independently of each other. Each extrusion may be depicted as a hanging U-tube with both openings at the bottom. The length of the 'tube', up to its U-turn, is about 13 m and the size of the openings is about 25mm x 80mm. What was the reason for your company to use the MBV method on the heat exchanger? Was it corrosion or only erosion? We have mineral and oxygen corrosion problem and I am still concerned about the possibility that the erosion remains the biggest problem. Thank you in advance for your comments.

Gregory Szewczyk
- Toronto, Ontario, Canada


2003

Dear Gregory

Sorry for long silence. The reasons for MBV comes from the need to protect the Al alloys from corrosion . as mentioned in my last letter first you have to chose appropriate alloy to get maximum coating thicknesses and erosion resistances. Unfortunately the MBV process can not be immersed at site. You need baths sized to accept the largest existed and dismantled components. Please inform us any how in order to start from alloys material selection ,pretreatment and post-treatment. The production rate of heat exchanger is also the main reasons to decide to invest for this type of coating. It is still the best practical way for al heat exchanger. In case if you need more information please do not hesitate to contact.

Hadi Khosravi
- Tehran, Iran


2003

Have you given any thought about purchasing pre-coated heat exchanger aluminum finstock? We supply pretreatments and coatings for the aluminum coil coating industry. Many of our customers sell their coated aluminum to coil forming shops that make air conditioners, etc. Precoated finstock will inhibit the galvanic corrosion you are describing. Lateral corrosion from the bare edge inward could be a concern depending on the environmental conditions but this mechanism usually takes several years to notice.

Mark Thompson
- Charleston, South Carolina



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