2.0 MODULAR SUPPORT TECHNOLOGY 2.4 CORROSION
Modular Support Systems Technical Guide , Edition 1
The following is an overview of typical finishes used on Hilti MT products . For more detailed information from Hilti on material finishes and corrosion protection , please consult the Hilti Corrosion Handbook which can be found under the Documents section for MT portfolio items on Hilti Online .
CORROSION HANDBOOK
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Outdoor Coating ( OC )
The Hilti MT OC System for outdoor applications has been developed with various corrosion protection technologies and consists of two finishes : Hot-Dipped Galvanized ( HDG ) and Zinc Magnesium ( ZM ). The Hilti OC is intended primarily for use in environments considered Outdoor with low pollution . For more corrosive environments , additional protection may be required . The proper amount of corrosion protection for a given application should always be assessed by the Design professional to ensure products meet the project requirements .
Hot Dipped Galvanized ( HDG )
Electro-Galvanized ( EG )
Electro-Galvanized , or zinc plated , bonds a minimum 0.5 mil zinc coating to carbon steel through an electrolysis process . Most Hilti MT connectors and miscellaneous hardware are available with an electro-galvanized finish . This coating is in accordance with DIN EN ISO 2081 .
Pre-Galvanized ( PG )
Pre-Galvanized parts are manufactured by passing sheet steel through a molten zinc bath . Afterwards , the sheets are cold-formed into applicable shaped profiles and slots are punched , hence the name “ pre-galvanized ". PG refers to pre-galvanized parts with punches slots and PGS refers to solid strut . Surfaces of the punched and cut portions are partially protected by the adjacent zinc plating which acts as a sacrificial anode impeding corrosion of the raw edges . However , if corrosion remains a concern additional protection may be required . PG conforms to ISO EN 10346 galvanizing , with a Z275 thickness ( 0.787 mils thick or 0.77 ounces zinc per square foot of steel ).
Component parts such as base plates and system connectors have zinc coatings applied by the hot-dipped galvanizing ( HDG ) process in accordance with the ASTM A153M Standard . On hot dipped galvanized parts , the zinc coating process occurs after cold forming and punching . The parts are pretreated , pickled , and then dipped into tanks of molten zinc . HDG provides increased corrosion resistance compared to PG and EG finishes . HDG conforms to ASTM A153 / A153M galvanizing as stated on the product sheet for beams , connectors , bases , splices , and fasteners . Suitability of a HDG finish for a product must be assessed for each project .
Zinc Magnesium ( ZM )
MT profiles such as strut , channels , and girders are coated with zinc-aluminum-magnesium alloy ( ZM ) by a continuous hot-dip galvanizing process during the steel coil phase in accordance with the EN 10346 Standard . On Zinc Magnesium parts , the process involves sheet metal coils that are drawn continuously through a bath of molten zinc after the surface has been cleaned and it is subjected to a special annealing process . In addition to zinc , the molten bath contains Magnesium ( Mg ) and Aluminum ( Al ). The Aluminum reacts with the steel surface to create a layer with a thickness of 0.984 mils per side ( 1.02 ounces per square foot ), which inhibits the formation of ZnFe phases . Hilti ’ s OC ZM processing conforms to the EN 10346 Galvanizing Standard .
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