dk nkf - Nordisk Konservatorforbund Danmark

Considering the changes of appearance of iron
and steel objects during conservation
Introduction
The “state of the art” in choosing protective coatings
for iron and steel in collections of newer history and
industrial heritage will be quite briefly presented.
Objects containing forged iron, steel and cast iron
alloys are in the following all designated as iron.
Possibilities and limitations for the use of clear and
semi-transparent coatings should be judged and
compared with protection of surfaces with several
paint layers. The choice is between protected,
painted surfaces looking very much as the original
by means of artistic retouch in the top layer or
considering whether a clear coating is protective
enough and can present and reveal an original metal
texture or ornamentation beneath. Clear coatings
can actually change an object’s looks just as varnish
layers do on paintings.
Both the conservation and ethical values involved
will be discussed. Thereby many aspects will be
covered quite briefly and picture examples will not
be fully debated. Discussion, with illustrations in
colour, will be part of the conference presentation.
It has not been possible to divide the following text as
in scientific articles. The starting point is sections on:
1) Corrosion rates according to climate condition
and iron surface, 2) General aspects of protecting
iron with coatings 3) followed by a case-story with
more considerations on display and conservation:
Testing a decision-making model. The last section:
Conclusion is short, relying on the hope that the
presented information will nourish the debate
between conservators together with historians and
conservation scientists.
The conservator and historian’s standard ethical
values for preservation and conservation are easy
to maintain if historical iron only needs a light
cleaning to remove dust from use or storage and is
Karen stemann-petersen
to be displayed or stored at low relative humidity.
For unprotected iron placed at higher humidity and
for iron with actively corroding surfaces, the same
professionals will, of course, wish to protect the
objects from rusting away, either by treatment or
removal from corrosive surroundings. For display
reasons, changing a sad and rust-stained object’s
appearance to something more presentable, may also
be considered. Taking the first step in a treatment
of iron and steel surfaces by removing rust layers
however allows more access for oxygen to the
corrosion zone and makes the metal surface more
instable. Follow-up treatments become necessary.
This paper deals with conservation considerations
for unstable iron objects that can not be placed at
low relative humidity and rust-coated, sad-looking
ones that are to be displayed.
Corrosion rates according to
climate condition and iron
surface
The corrosion rate of iron depends on climate
conditions as well as the condition of the metal
surface. The information in this section combines
of general knowledge of corrosion science,
conservation and experience. In preparation of the
paper, there has not been time for a new literature
review.
Conservators, as well as corrosion scientists, must
consider the changes in stability of iron if it is moved
to an area with a different climate or its surface is
treated. Conservators can sometimes be involved in
some cleaning of iron surfaces without facing the
facts or having the necessary discussions with the
involved curator or institutional customer. Before
actions are taken on either large or small historical
iron objects, a decision-making model should be
applied so that all the facts are considered.
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