Lime milk is a suspension of calcium hydroxide in water. According to my references, lime milk is compatible with 316L stainless steel. Some pitting may occur at elevated temperatures. When austenitic stainless steels like 316L corrode, they usually do so by means of a form of localized corrosion like pitting, stress corrosion cracking, intergranular attack, etc. Since a corrosion allowance is only helpful when uniform corrosion can occur, corrosion allowances typically offer no benefit when dealing with austenitic stainless steels.