Technical Session 12: Engineering Session
Harvey Claussen, The Zythos Project LLC, Portland, OR, USA
ABSTRACT: Creating and maintaining a suitable non-reactive
surface for brewery vessels requires an understanding of the nature of
austenitic stainless steels. The selection of the appropriate chemical
and electrochemical system for passivation is critical. All of this can
be brought into perspective for the brewer. An example is the
composition of the surface during passivation of molybdenum containing
austenitic stainless steels such as Avesta AB with 3.6 a/o Mo and
Sandvik AB with 1.7 a/o Mo in 0.1M HCl + 0.4M NaCl. Low
levels of chlorides can seriously alter the nature of the seemingly
inert coating. The alloys exposed to certain electrolytes under
polarization can develop varying corrosion potentials, as well as active
and passive potentials. Electrochemical polarization can vary depending
on the initial voltaic potential, as well as the rate of an increasing
potential. Ni and Fe cations can be present to varying degrees in the
oxide. An enrichment of Ni by 10 a/o may also develop on the surface of
the metallic phase. At the passive region, the film formed on the alloy
can be chromium oxide. Bringing all of the passivation technology
together can be daunting, so the presentation focuses on a simplified
approach to the understanding of passivation technology.
Harvey
Claussen received a B.S. degree in chemical engineering from the
University of Washington in Seattle. He has been involved with the
design, construction, and operation of fine chemical, agricultural, and
food facilities since 1961. He first entered the brewing world in 1984,
siting and designing microbreweries. In addition, Harvey enjoys home
brewing when time permits. He and his associates founded The Zythos
Project LLC, a beer think tank, in 2011.
VIEW PRESENTATION 43
