The automobile industry continues to put pressure on the heat
exchanger manufacturing sector to develop heat exchangers that are of less than
average dimension, light, efficient, and as affordable as possible. During the
service life, automotive heat exchangers are subjected to a variety of
environments, including heating and cooling cycles, saltwater environment on
the road surface, and mechanical loading. As a result, corrosion performance is
critical, as perforation of the material could result in system failure. The
corrosion behaviour of roll-bonded aluminium brazing sheets is significant
since this is the most common mode of failure for automotive heat exchangers,
especially with the trend toward lighter automotive parts. Furthermore, thermal
treatments such as solution heat treatment, homogenization, and brazing alter
the microstructure and, as a result, vary the corrosion behaviour. The
qualities of the finished product, such as mechanical properties and corrosion
resistance, are impacted by microstructural variation in AA3xxx that results in
the development of manganese (Mn) bearing dispersoids during preheat treatment
before rolling. The effect of homogenization temperature and duration on the
microstructure of AA3xxx aluminium alloys has been studied, but more research
is needed. The goal of this investigation was to see how different holding
times during pre-heat treatments affect the corrosion behaviour of the
AA4045/3003 modified brazing sheet used for automotive heat exchangers. The
experimental plate samples were made from modified alloy 3003 and standard
alloy 4045 in the cast and homogenised state. Accelerated laboratory corrosion
tests are essential for ranking trial materials and ultimately qualifying an
alloy for production. The corrosion behaviour of one-layer modified AA4045/3003
brazing sheets was examined in this chapter before brazing. The samples
homogenized for 20 hours exhibited more corrosion resistance with a corrosion
rate of less than 0.1 mm/y than those homogenized for longer times. The
corrosion resistance deteriorated with an increase in the homogenization time.
The corrosion propagation was attributed to potential differences between the
brazing sheet, creating a galvanically driven perforation of the core material
by the diffusion zone after accelerated salt spray testing (ASST) and
electrochemical testing.
Author
(s) Details
JS Moema
Advanced Materials Division, MINTEK, Randburg, South Africa and Department
of Material Science and Metallurgical Engineering, The University of Pretoria,
Private Bag X20, Hatfield Campus, Pretoria 0028, South Africa.
T Ramathe
Department of Material Science and Metallurgical Engineering, The
University of Pretoria, Private Bag X20, Hatfield Campus, Pretoria 0028, South
Africa.
CW Siyasiya
Department of Material Science and Metallurgical Engineering, The
University of Pretoria, Private Bag X20, Hatfield Campus, Pretoria 0028, South
Africa.
NDE Hadebe
Advanced Materials Division, MINTEK, Randburg, South Africa.
T Buthelezi
Hulamin Operations Proprietary Limited, Moses Mabhida Road,
Pietermaritzburg, 3201, South Africa.
Please see the book here:- https://doi.org/10.9734/bpi/cmsdi/v6/2009
