Specs for ASTM A153 AND ASTM A194-2005a

Sir,
What is the difference between ASTM A153 AND ASTM A194-2005a

The 'Scope' of each ASTM specification is available at http://www.techstreet.com & www.astm.org
See ASTM A153 [link is to "Download ASTM Standards" from ANSI.org] , 'Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware' and ASTM A194 [link is to "Download ASTM Standards" from ANSI.org] , 'Standard Specification for Carbon and Alloy Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both.'

Any coating of fasteners, and whether nut threads are cut before or after coating, must be specified in the ASTM A194 manufacturing process. An * suffix added to the nut grade indicates zinc coating. ASTM A153 provides a nominal zinc thickness of 43 microns on small (3/8" or 9.52 mm diameter) fasteners, 53 microns on larger.

Also, zinc coated fasteners should only be used at temperatures below 390 °F [210 °C] to avoid possible embrittlement (per Appendix X2 of A194).