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PureTemp 23 shows no corrosive effect on five metals tested in study


The biobased phase change material does not corrode aluminum, copper, carbon steel, stainless steel 304 or stainless steel 316.

PLYMOUTH, Minnesota – PureTemp 23, one of 19 PureTemp phase change materials recently certified as 100 percent biobased by the U.S. Department of Agriculture, has been shown to have no corrosive effect on five metals tested in a study by Spanish researchers.

Because of their ability to absorb and release large amounts of thermal energy, phase change materials (PCMs) are increasingly being used to boost the efficiency of cooling and heating systems in residential and commercial construction. PCMs must be compatible with the material used to contain them, and the ideal container must be lightweight and highly conductive.

For this study, researchers from the University of Barcelona and the University of Lleida selected five metals with such properties: aluminum, copper, carbon steel, stainless steel 304 and stainless steel 316. The metals were immersed in four different PCMs (one inorganic mixture, one biobased and two fatty acid eutectics) for various periods and then examined for evidence of corrosion.

Two of the PCMs tested are commercial formulations: Rubitherm’s SP21E, with a melting point of 21º Celsius, and Entropy Solution’s PureTemp 23, with a melting point of 23º Celsius. The other two, prepared at the University of Lleida, were fatty acid eutectics with similar melting points.

Highlights of the 12-week study:

  • PureTemp 23 does not corrode any of the studied metals.
  • Stainless steel 304 and stainless steel 316 are resistant to all four PCMs.
  • Aluminum should be avoided as an SP21E container.
  • Copper is corroded by both fatty acid eutectics.
    The researchers concluded that PureTemp 23 is suitable for long-term containment in aluminum, copper, carbon steel, stainless steel 304 and stainless steel 316. They recommended caution in using carbon steel to contain SP21E but noted that the stainless steels and copper showed great resistance to the salt-based PCM’s corrosive effects. They also recommended caution in using copper for long-term containment of the eutectic PCMs but found that material to be compatible with the other four metals.

    One of the study’s authors, Dr. Luisa F. Cabeza of the University of Lleida, is a leading authority on thermal energy storage. She is the director of GREA Innovació Concurrent, a research group that is developing thermal energy storage concepts and systems. She recently joined Entropy Solution’s board of advisors.

    The study will be published in the journal Renewable Energy in April. See

    About Entropy Solutions Inc.

    Entropy Solutions is a biobased specialty chemical company with offices in Plymouth, MN, and Tuscaloosa, AL. Its PureTemp PCM technology is the world’s first 100 percent renewable-based phase change material. Entropy partners with leading product development companies in the shipping, construction, textile, health care and alternative energy industries, among others. PureTemp has received global recognition, including the DuPont Diamond Innovation Award, and recently earned biobased certification from the USDA. To learn more, visit

    Media contact

    Ben Welter
    Entropy Solutions