Engineering FAQs

6.7.3. What is the difference between the surface preparation requirements for Class A, B, and C slip resistance in slip-critical connections?

With uncoated faying surfaces, clean mill scale provides a Class A slip resistance (μ=0.33), whereas blast cleaning is required to obtain the higher Class B slip coefficient μ=0.50. With painted faying surfaces, the slip resistance is determined by the tested performance of the paint system as meeting Class A, B, or some other intermediate slip coefficient and the steel to be painted must be blast-cleaned in all cases. Class C surfaces are roughened (see 6.7.4) hot-dip galvanized surfaces that provide a slip coefficient μ=0.35. This current value, taken from the RCSC Specification, is lower than the historically permitted slip coefficient of 0.40.

last modified 28 August 2002