Certain chemicals, ferric, alum, and hydrochloric acid, are inherently high temperature chemicals. To avert catastrophic failure of a tank, a margin of safety is required to manage risk.
High-density cross-linked polyethylene, XLPE, is designed to withstand temperatures up to 150 degrees Fahrenheit, 10-15 degrees higher than standard linear polyethylene. XLPE is more rigid. It will hold its form and shape at higher temperatures, and the likelihood that the poly will flow again is nonexistent.
While XLPE can withstand 150 degree heat, and even higher temperatures, with a margin for safety without catastrophic failure, we recommend XLPE tanks exposed to over 150 degree heat be removed from service to avoid potential future issues with your tank.
Custom storage solutions and installations in high temperature environments are possible using XLPE. Please refer to the ASTM D1998, page 6, for specific temperature stress factors using XLPE.