Aluminum Thru Wall Scupper Question

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Author Message Jerome J. Lazar, RA, CCS, CSI, NCARB Senior Member Username: lazarcitec Post Number: 1867 Registered: 05-2003 Posted on Wednesday, April 04, 2018 - 05:37 pm:    How to protect aluminum scupper from corrosion when aluminum is in touch with concrete or concrete block? David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1644 Registered: 03-2002 Posted on Wednesday, April 04, 2018 - 07:21 pm:    Bituminous coating on the backside? David G. Axt, CCS, CSI, SCIP Specifications Consultant Axt Consulting LLC Jeffrey Wilson CSI CCS SCIP Senior Member Username: wilsonconsulting Post Number: 250 Registered: 03-2006 Posted on Wednesday, April 04, 2018 - 07:39 pm:    I always recommend against using aluminum in contact w/ concrete or msry, since it's difficult to ensure that it will be properly isolated. In addition, joints in aluminum scuppers are usually sealed, making them prone to failure. Stainless-steel or another weldable metal solves both shortcomings, so that's what I always suggest to my clients. Jeffrey Wilson CCS CSI SCIP Wilson Consulting Inc Ardmore PA Jerome J. Lazar, RA, CCS, CSI, NCARB Senior Member Username: lazarcitec Post Number: 1869 Registered: 05-2003 Posted on Wednesday, April 04, 2018 - 09:31 pm:    Bituminous Coating has certainly been the "industry standard", but its messy to use, Contractors hate using it so sometimes they use nothing. Stainless steel is expensive, I spec stainless on the high end, luxury projects. Galvanized metal does not last long in South Florida, with all the salt in the air. Therefore I am looking for a coating that is relatively easy to apply, and "inexpensive". For a while I was specifying SW Loxon, but SW won't warranty the use. Latest possibility is a Fast Cure Epoxy like SW Macropoxy. Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 2146 Registered: 07-2002 Posted on Wednesday, April 04, 2018 - 09:38 pm:    Automotive paint? Jerome J. Lazar, RA, CCS, CSI, NCARB Senior Member Username: lazarcitec Post Number: 1871 Registered: 05-2003 Posted on Wednesday, April 04, 2018 - 10:07 pm:    Lynn, I am not a car geek, care to be more specific? Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 2147 Registered: 07-2002 Posted on Wednesday, April 04, 2018 - 10:29 pm:    Seriously, paint used on the exterior of a car, a lot of which is aluminum, and withstands pretty much anything that can be thrown at a car. Except maybe another car. You can get touch-up paint in spray cans. Candy-apple red, anyone? Jerome J. Lazar, RA, CCS, CSI, NCARB Senior Member Username: lazarcitec Post Number: 1873 Registered: 05-2003 Posted on Wednesday, April 04, 2018 - 11:44 pm:    Water based acrylic polyurethane paint is the most popular automotive paint, my SW Rep is looking into a spec. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 864 Registered: 01-2008 Posted on Thursday, April 05, 2018 - 09:44 am:    Lynn, My favorite color. My 2016 H-D road king is candy-apple red. James Sandoz, AIA, CSI, CCS, CCCA Senior Member Username: jsandoz Post Number: 236 Registered: 06-2005 Posted on Thursday, April 05, 2018 - 10:26 am:    I've had polyamide epoxy coatings recommended instead of bituminous coatings. They are two-part like many epoxies but are easier to work with than bituminous coatings and probably more environmentally friendly. I've been specifying polyamide epoxy for aluminum in contact with cementitious materials for a few years now and have had no push back from contractors. That doesn't necessarily mean they are following the specification. :-( One example of the product is Sherwin-Williams ArmorSeal 1000HS. David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1645 Registered: 03-2002 Posted on Thursday, April 05, 2018 - 12:48 pm:    How about strips of self-adhered asphalt (or butyl) based membrane (Henry Blueskin, Grace Vycor, et.)? It is easy to apply (no waiting for coatings to dry) and the installer probably already has it in their truck. David G. Axt, CCS, CSI, SCIP Specifications Consultant Axt Consulting LLC Dewayne Dean Senior Member Username: ddean Post Number: 156 Registered: 02-2016 Posted on Thursday, April 05, 2018 - 03:04 pm:    I like David's idea. Dave Metzger Senior Member Username: davemetzger Post Number: 727 Registered: 07-2001 Posted on Thursday, April 05, 2018 - 03:35 pm:    Self-adhered asphaltic membranes sound OK, clean solution, as long as they are on fully-concealed surfaces of the scupper; the membrane will degrade on prolonged exposure to UV. Also, it will act as a bond-breaker with concrete, so need to detail accordingly Wayne Yancey Senior Member Username: wayne_yancey Post Number: 865 Registered: 01-2008 Posted on Thursday, April 05, 2018 - 04:24 pm:    I know we are refering to aluminum, the American Galvanizers Association states: "Paint is not a reliable method of deterring the return current path of the galvanic cell; rubber or some other insulating material would be best for that." As David wrote, a rubberized self-adhered membrane. Wayne Brian E. Trimble, CDT Senior Member Username: brian_e_trimble_cdt Post Number: 100 Registered: 08-2005 Posted on Thursday, April 05, 2018 - 04:30 pm:    Aluminum is reactive in the presence of "fresh" concrete or mortar. I am not sure how reactive it is when the concrete or mortar has cured. I believe it is the free alkakis that could create a problem, but once the concrete or mortar has cured I don't think it would be as much of a problem. Putting any kind of coating may be enough. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1743 Registered: 03-2002 Posted on Friday, April 06, 2018 - 11:14 am:    I always spec'd what David suggested - peel and stick sheets. It's easy to get, easy to do, and reliable. Jerome J. Lazar, RA, CCS, CSI, NCARB Senior Member Username: lazarcitec Post Number: 1874 Registered: 05-2003 Posted on Friday, April 06, 2018 - 11:39 am:    Thanks for all the input, I am going to provide 4 possible solutions: Bituminous Paint Epoxy Paint Water-white methacrylate lacquer (called out in the Building Code or Self Adhered WP Membrane let the GC select the product.