What material for a thin riser?

I wish to rebuild a riser for my small rocket heater and i need sugestions for a material thats suited for just a 2 cm ( 1 in)wall thickness.
I was thinking at stainless steel filled with something,eyther perlite or LECA ( expanded clay balls) or even crushed Ytong bricks.
However i wouldnt like to use stainless steel in the riser because in my experience it rusts after a week.Not much rust but it does rust .

I have somme of that edible white Kaolin at home .It seems its the highest temp resistant but not sure i will be able to get it to the hardening point of 1800C.
I was thinking to mix it with perlite but the perlite might melt before the clay hardens.
https://www.thesprucecrafts.com/clay-basics-2746314

Mihai Ilie wrote:I wish to rebuild a riser for my small rocket heater and i need sugestions for a material thats suited for just a 2 cm ( 1 in)wall thickness.
I was thinking at stainless steel filled with something,eyther perlite or LECA ( expanded clay balls) or even crushed Ytong bricks.
However i wouldnt like to use stainless steel in the riser because in my experience it rusts after a week.Not much rust but it does rust .

1” thick ceramic fiber board is working for us. A bit on the expensive side of materials but works really good. Easy to cut and install.

Hope that helps...

Cheers, Peter🏔👨🏻‍🔬🏔

Hi Mihai;    A five minute riser is what you need.    
Ceramic fiber blanket in a steel pipe.   1" thick. capable of withstanding temperatures over 2000 F

Here is a link to a post all about it.  https://permies.com/t/95849/Working-Morgan-Superwool-ceramic-blanket