Direct Fastening Technical Guide , Edition 24
3.6.1.6 CORROSION RESISTANCE GUIDELINES
Self-drilling screw fastener selection guidelines 1 , 2 , 3 , 6 , 7
Environment |
Low indoor - dry : no moisture exposure |
Medium indoor and exterior - dry : minimal moisture exposure |
High indoor and exterior - wet : Heavy industrial or coastal areas with high prolonged moisture levels but no direct exposure to chlorides , and average temperatures below 86 ° F ( 30 ° C ). |
Connection type
Screw fastener descriptions
Screw fastener designation
Product technical guide section
Untreated lumber-to-steel , steel-to-steel , gypsum-to-steel applications
Hardened carbon steel fasteners with electro-galvanized ( min . 5 - 13 microns ), black or grey phosphate coatings
Hilti Zinc Plated Screws , Hilti Dark Grey Phosphate ( DGP )
Section 3.6.2 or 3.6.3
Pressure-treated 4 or fire-retardant lumber-to-steel ; aluminum-to-steel ; dissimilar metals
Carbon steel , two-step heat treated fasteners with Kwik-Cote coating
Hilti Kwik-Flex
Section 3.6.4
Untreated lumber-to-steel , steel-to-steel , gypsum-to-steel applications ; cement board-to-steel
Hardened carbon steel fasteners with Kwik-Cote or Duplex coating
Hilti Self-Drilling Screws with Kwik-Cote , CRC , or Kwik-Seal designation
Section 3.6.2
Pressure-treated 4 or fire-retardant lumber-to-steel ; aluminum-to-steel ; dissimilar metals
Carbon steel , two-step heat treated fasteners with Kwik-Cote coating
Hilti Kwik-Flex
Section 3.6.4
Untreated lumber-to-steel , steel-to-steel , gypsum-to-steel applications
Pressure-treated 4 or fire-retardant lumber-to-steel ; aluminum-to-steel ; dissimilar metals
300 series 5 stainless steel fastener
Hilti Bi-Metal Kwik-Flex
Section 3.6.5
1 If the moisture content of Pressure-Treated Lumber is high (> 18 %) or unknown , stainless steel fasteners are recommended . Select appropriate stainless steel grade for your application .
2 Guidelines based on fastener coating / material resistance to environmental corrosion ( commonly called rusting ) and fastener hardening process / resistance to hydrogen assisted stress corrosion cracking ( HASCC ). Evaluate site conditions which may affect these guidelines , such as : corrosive agents other than those listed ; expected service life ; other ( non-environmental ) types of corrosion , etc .
3 In highly corrosive environments ( such as direct exposure to chlorides with average temperatures above 86 ° F ( 30 ° C )) it is generally recommended that a Highly Corrosive Resistant ( HCR ) fastener be used . Contact Hilti Technical Support at 877-749-6337 for more information . 4 Pressure treated lumber refers to lumber such as SBX / DOT , Zinc borated ACQ , CA-B , CBA-A treated lumber . 5 300 series recommended . Most 400 series stainless steels , such as 410 stainless steel , 410 super-passivated stainless steel and 400 modified stainless steel are generally considered susceptible to HASCC . Moreover , these grades of stainless steel are 18 / 0 – they contain chromium but no nickel which reduces corrosion resistance significantly when compared to 18 / 8 grades ( 302 , 304 ) or 18 / 8 / 2 grade ( 316 ). 6 The decision as to which fastener optimally meets the demands of a specific application is ultimately the judgment of the Engineer of Record or other responsible person for the project . 7 Reference Section 2.3.3.1 for more information on corrosion resistance .
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