Im doing a bit of worldbuilding involving some molluscs in an alkaline lake. I read that plastics are resistant to base corrosion and later that some plastics such as polyethylene can be produced using organic materials such as ethanol from fermentation. I was thinking that these molluscs could ferment consumed plants and produce polyethylene in their bodies to create a base-resistant shell that would help them survive. (old content) Along with some other adaptations, I am wondering if they could viably develop shells made of a material resistant to base corrosion and would like some real life examples.