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

Selected Application Recommendations
Radioactive Materials
Polymer-matrix composites in general have a very low
neutron cross-section capture effi ciency. Therefore, they
are very well-suited to the containment of radioactive
materials, even at relatively high levels of radioactivity.
Testing of uncured DION ® 382 by Atlas Chemical
Laboratories demonstrated that this resin is highly
resistant to molecular weight changes at dosages up
to 15 million rads. Extrapolations based on this study
estimate that DION ® 382 may be able to withstand 50
to 100 million rads. For reference, the lethal radiation
dose is about 400 rads. Given the hazardous nature of
radioactive materials, testing is recommended before
actual use in high radiation environments.
Sodium Hydroxide and Alkaline Solutions
Alkaline solutions can attack the resin, usually by
hydrolysis of any ester groups. Glass fi bers and other
silica based materials can also be attacked or digested.
This leads to a very characteristic type of wicking and
blistering, as well as fi ber blooming. Dilute sodium
hydroxide is often more aggressive than the more
concentrated solutions. This relates to the fact that
NaOH is a very strong base, but at higher concentration
there is equilibrium between dissolved and solid phase
NaOH, which reduces the caustic effects. Epoxy based
vinyl esters and bisphenol-A based polyesters display
exceptional resistance to caustic.
Even though novolac based vinyl esters are wellregarded
for excellent corrosion and thermal resistance
in many applications, it is often observed that novolac
based resins can show somewhat inferior caustic
resistance. Laminates based on novolac vinyl esters
exposed to caustic have a tendency to develop a pinkish
color incipient to failure. It is speculated this is due to
formation of phenolates from the novolac structure.
There is widespread belief that it is advisable to use
synthetic surfacing veils versus C-glass in caustic
applications. However, controlled laboratory tests
usually reveal no clear-cut or distinct advantages to a
synthetic veil, and there is a long history of use of C-veil
in alkaline environments.
The synthetic veil allows an increased resin content at
the surface to ostensibly afford more protection. On the
other hand, the resin rich areas can make the surface
more prone to cracking and can, at times, present more
fabrication diffi culties.
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