BOS ISO TR 10217_1989

Description

This Technical Report provides a discussion of the Parameters that have a bearing on the internal corrosion of solar water
heating Systems.
The following topics are not dealt with in this Technical
Report :
The following topics are not dealt with in this Technical
Report :
– Problems of compatibility between polymeric materials
(plastics and rubber) and fluids;
– corrosion risks concerning the enclosure and the
external surface of the absorber;
– safety and health questions, especially the toxicity of
heat-transfer fluids.
In many fields, the corrosion Problem is hard to deal with,
because it overlaps several matters. As far as solar Systems are
concerned, corrosion prevention cannot be treated only in
respect of a component, or only as a durability Problem, or only
as a design Problem. lt cannot be solved only by specific tests,
or only by design recommendations.
This Technical Report addresses the question of which requirements
are necessary, to predict with confidence long
failure-free lifetimes in active solar Systems, from the Point of
view of internal corrosion. lt gathers information provided in
previous Papers on this subject Iespecially bibliography
references 2, 3 and 4) while staying in agreement with them.
2 Corrosion risk Statement
If corrosion effects are considered as a reliability Problem for
the System, because corrosion tan reduce the quality of the
System, the following Points may be detailed.
2.1 The degradating agent is internal corrosion. Its effects
are different according to
– materials;
– couples of materials;
– temperature;
– fluid circulation;
– fluid Oxygen content;
2.2 The materials concerned are
– absorber materials;
– pipes and fitting materials;
– fluids;
– welding materials.
2.3 The functional characteristics of the System are
– pressure resistance;
– efficiency of thermal transfer between the sun and the
storage;
– high and low temperature resistance.
2.4 The failure modes (i.e. the ways for the degradating
agent to act on the materials to weaken their functional
characteristics or those of the System) are
– bad design choice (materials and conditions of use of
the System);
– degradation of materials during Service life;
3 Discussion
Internal corrosion darnage in solar Systems is generally detected too late: it is reported as a serious Problem, which requires
replacement of significant Parts of the System [SI, but inspection studies [Q 131 give little information on this subject; a visual
inspection, even completed by user-consultation, is not able to show the growing effects of internal corrosion before the first
pitting occurs.
Among the types of darnage reported, most are related to the use of aluminium absorbers without precautionsW
Several documents treat the corrosion Problem as presented previously : it is a whole-System Problem, and initial design and
material-choice recommendations are emphasized as a way to prevent corrosion damage[z! 111. Even in Standards, the problem
is sometimes left to expert advice[W A table of acceptable or unacceptable conditions tan summarize all the data
given about installation Parameters, metaI/fluid pairs and metal association 11I 41.