Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
(OP)
I've been given the task in looking into fastener alternatives that our company can use to attach 6063-T6 Aluminum Extrusions to various substrates with different grades of carbon steel fasteners.
The particular application I'm looking at applying this fasteners in are for Drained/Back Ventilated cladding systems where an electrolytic liquid will be present and galvanic corrosion becomes one of primary design issues. We've typically been using SAE Grade 5 Dril-Flex fasteners (typically a curtain wall industry standard, see link below for specifics), however I'm looking into exploring the use of SAE grade 1 Buildex TEK fasteners with a bonded neoprene washer to help minimize the dissimilar metal interaction (see link below).
Before I suggest performing a salt spray test to compare these two fasteners would anyone expect to see similar results due to the neoprene washer between the materials?
Elco Dril-Flex Fastener Informatoin
-http://www.elcoconstruction.com/drilflex.asp
-http://files.engineering.com/getfile.aspx?folder=2ad29fba-bbc0-4dcf-8b41-162b535f6293&file=Stalgard_Silver_Spec.doc
Buildex TEK Fastener Data
-http://www.itwbuildex.com/bondedtek.htm
Thank you in advance for your input!
The particular application I'm looking at applying this fasteners in are for Drained/Back Ventilated cladding systems where an electrolytic liquid will be present and galvanic corrosion becomes one of primary design issues. We've typically been using SAE Grade 5 Dril-Flex fasteners (typically a curtain wall industry standard, see link below for specifics), however I'm looking into exploring the use of SAE grade 1 Buildex TEK fasteners with a bonded neoprene washer to help minimize the dissimilar metal interaction (see link below).
Before I suggest performing a salt spray test to compare these two fasteners would anyone expect to see similar results due to the neoprene washer between the materials?
Elco Dril-Flex Fastener Informatoin
-http://www.elcoconstruction.com/drilflex.asp
-http://files.engineering.com/getfile.aspx?folder=2ad29fba-bbc0-4dcf-8b41-162b535f6293&file=Stalgard_Silver_Spec.doc
Buildex TEK Fastener Data
-http://www.itwbuildex.com/bondedtek.htm
Thank you in advance for your input!





RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
First, are you aware that Elco also provides fasteners with EPDM sealing washers? Their product is called Flo-Seal®:
http://www.elcoconstruction.com/floseal.asp
Second, I prefer the Stalgard® coating from Elco (zinc rich basecoat, Al-rich topcoat) to Climaseal® from ITW (mechanical Zn plating + dip-spin thermoset polyester topcoat). It is better for bimetallic corrosion where Al & steel are the mating pieces.
Regarding your original question, the EPDM washer will certainly improve the corrosion performance of the finished assembly, because it provides an isolator between the Al and steel pieces, and increases the distance that any electrolyte must bridge between the two disparate metals. Testing just the fastener by itself in a salt spray environment will not show any real difference, unless you are intending to compare the nominal corrosion resistance of the Stalgard® coating vs. the Climaseal® coating, in which case the results will be moot because it is the system performance that is important, not the fastener in isolation.
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
The overall goal is to have a cladding system that will not only be structurally sound but also provide adequate resistance to galvanic corrosion.
My next question stemming from this discussion is would there be a marked difference in the effective lifespan if the Buildex with Bonded washers were used instead of Dril-Flex?
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
Metal Coatings Corporation - Houston TX
http://www.metcoat.com
RE: Galvanic Corrosion between Aluminum Extrusion and Steel Fastners
I hope this answered your question.