CORROSION GUIDE 181108_new table content format ... - Reichhold

Selected Application Recommendations
Biomass and Biochemical Conversion
Applications have been increasing for processes
which transform biomass or renewable resources into
usable products. Most of the impetus has been energy
related, but the technology has diverse relevance, such
as various delignifi cation processes associated with
elemental chlorine-free pulp production. Raw materials
include things like grain, wood, agricultural or animal
wastes, and high cellulose content plants.
Sometimes the processes involve pyrolysis or
gasifi cation steps to break down the complex molecules
of the biomass into simpler building blocks such as
carbon monoxide or hydrogen, which in turn can be
used as fuels or catalytically synthesized into other
products, such as methanol. However, the most common
biochemical conversion process is fermentation, in
which simple sugars, under the mediation of yeasts or
bacteria, are converted to ethanol. With lingo-cellulose
or hemicellulose, the fermentation must be preceded by
thermochemical treatments which digest or otherwise
render the complex polymers in the biomass more
accessible to enzymatic breakdown. These enzymes
(often under acidic conditions) then enable hydrolysis of
starches or polysaccharides into simple sugars suitable
for fermentation into ethanol. Many of the conversion
steps have other embodiments, such as the anaerobic
digestion to produce methane for gaseous fuel.
A great deal of technology and genetic engineering is
evolving to enable or to improve the effi ciency of these
processes. It is expected that many of the process
conditions can often be quite corrosive to metals, and
FRP composites can offer distinct benefi ts.
Bleaching Solutions
Bleach solutions represent a variety of materials
which display high oxidation potential, These include
compounds or active radicals like chlorine, chlorine
dioxide, ozone, hypochlorite or peroxide. Under most
storage conditions these materials are quite stable, but
when activated, such as by changes in temperature,
concentration, or pH, the bleaches are aggressive and
begin to oxidize many metals and organic materials,
including resins used in composites. Thus, resins
need to display resistance to oxidation as well as to
the temperature and pH conditions employed in the
process. Most interest centers on bleaching operations
employed in the pulp and paper industry, but similar
considerations apply to industrial, disinfection, and
water treatment applications.
Bleach solutions are highly electrophilic and attack
organic materials by reacting with sources of electrons,
of which a readily available source is the residual
unsaturation associated with an incomplete cure.
Consequently, the resistance of composites to bleach
environments demands a complete cure, preferably
followed by post-curing. Since air-inhibited surfaces are
especially susceptible to attack, a good paraffi nated
topcoat should be applied to non-contact surfaces,
including the exterior, which may come into incidental
contact with the bleach.
BPO/ DMA curing systems are sometimes advocated
for composites intended for bleach applications due to
concerns over reaction with cobalt promoter involved
in conventional MEKP/ DMA curing systems. While
BPO/ DMA curing can offer appearance advantages,
the conventional MEKP/ cobalt systems yield very
dependable and predictable full extents of curing and
thus have a good history of success.
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