Stainless Bolts

February 15, 2016 by · Leave a Comment 

304 Stainless Bolts – ASTM A193 Grade 8 Bolts

Grade 304 Bolting is the standard “18/8” stainless; it is the most versatile and most widely used stainless steel bolting, available in a wide range of bolting products.

Corrosion Resistance

Stainless Bolts are excellent in a wide range of atmospheric environments and many corrosive media. Stainless bolts are subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Commercial Stainless bolts are considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures.

Heat Resistance

304 Stainless bolts have good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. 304 stainless bolting in continuous at the 425-860°C range is not recommended if subsequent corrosion resistance is important.

316 Stainless Bolts – ASTM A193 Grade 8M

The grade 316 stainless bolt is the standard molybdenum-bearing grade, above the corrosion resistance of 304 bolts within the austenitic stainless steels. The molybdenum gives 316 stainless bolts better overall corrosion resistant properties than Grade 304 bolting, particularly higher resistance to pitting and crevice corrosion in chloride environments.

Corrosion Resistance

316 Grade 8M bolts are excellent in a wide range of atmospheric environments and corrosive media and are generally more resistant than 304. 316 Grade 8M bolts are subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Grad 8M bolts are considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures.

316 is usually regarded as the standard “marine grade stainless steel bolting”, but it is not entirely resistant to sea water. In many marine environments at elevated temperatures 316 bolting does exhibit surface corrosion, usually visible as brown staining.

Heat Resistance

Grade 8M bolts exhibit good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 316 bolts in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important.