Sclerotisation is present in all arthropods and is commonly referred to as ‘tanning’, which is derived from how the process darkens the cuticle as a side effect.
This process is simply the formation of covalent bond cross‑links between protein molecules, which dramatically increases the overall strength and rigidity of the cuticle.
Mineralisation is another method by which arthropods strengthen their exoskeleton, but it is generally only exploited by crustacea and diplopods (millipedes).
It is achieved by impregnating the cuticle with calcium salts, usually calcium carbonate.