Abstract
Research and/or engineering questions/objective
In air conditioning system, evaporator is the heat exchanger allowing to cooling air for passenger comfort and to condensate water. In the field, water condensation, hot and humid climatic conditions and some conditions allowing copper pollution generate early leak of the evaporator and air conditioning cooling break.
The evaporator is composed of brazed aluminium plate and fin, coated for hydrophilicity and bad smell prevention, without any specific anticorrosion function.
The aim of this paper is to demonstrate if the surface coating including anticorrosion function would increase significantly the life time of the evaporator, in real field simulated conditions.
Methodology
The corrosion test – called HEREL – was defined in order to simulate some severe corrosive conditions observed in the field: hot and humid climatic conditions, copper pollution. Two families of evaporators were studied. First family is the evaporator coated with hydrophilic and antimicrobial varnish. Second family is coated with a new developed anticorrosion, hydrophilic and antimicrobial conversion coating. These two families of evaporators have been submitted to the so called HEREL test, the pitting depth curve versus exposure time in test and the failure time in test were compared.
Results
Pitting depth curve versus exposure time in the so called HEREL test shows a 3 step corrosion mechanism: corrosion initiation, steady corrosion state, corrosion propagation in the brazed core aluminium. Comparison of the curves between the two families of coating shows a decrease of pitting depth in the corrosion initiation stage, and a delay on the second and third corrosion stages, for the evaporator family including anticorrosion function in the surface coating. Moreover a significant difference in the life time in test for the evaporator including anticorrosion function in the surface coating was measured of more than 50 days.
Limitation of this study
The corrosion test used in this study is one of the corrosive conditions observed in the field. This study doesn’t argue that all the corrosion conditions observed in the field and leading to evaporator leak are represented in the defined test conditions
What does the paper offer that is new in the field including in comparison to other work by the authors
This paper allows estimating the life benefit of a new surface coating concept in a corrosion reliability test reproducing some real severe conditions.
Conclusions
Anticorrosion surface coating allows a significant life time benefit of the evaporator in the severe corrosion conditions reproduced from the field.
Key Words Brazed evaporator, aluminium, surface coating, corrosion, reliability