Aluminum Roof Coating Questions
What contractors and building owners actually ask us about aluminum.
Aluminum-Specific Questions
Why does aluminum need a primer when blasted steel does not?
Because aluminum re-oxidizes almost immediately. Blasted steel presents clean metal that polyurea can bond to directly. Cleaned aluminum grows a fresh oxide skin within minutes, and a coating applied to that skin is bonded to the oxide, not to the metal — so it releases in sheets later. 7001 Primer is formulated to key through that thin fresh oxide, and it must go on in the same working session as the abrasion.
Can I just blast the aluminum harder to get a better profile?
No, and this is the most common mistake we see. Aluminum roof panel is typically 0.024" to 0.040" thick. An SSPC-SP6 commercial blast that is perfectly appropriate on structural steel will oil-can the panel, distort the ribs, and can perforate thin sheet. Aluminum wants a degrease followed by a uniform matte from a low-pressure brush-blast or abrasive pad — then primer, promptly.
How does the coating deal with all that thermal movement?
By stretching instead of resisting. OR-80SLM elongates 300–400% with tear strength in the 400–500 pli range. A 100-foot aluminum panel run moving close to an inch across a seasonal swing is a fraction of a percent of strain on the membrane. It is well inside the elastomer's working range, which is why it does not crack at seams and end laps the way rigid films do.
Will a coating actually stop galvanic corrosion at steel fasteners?
Yes, by removing the electrolyte. Galvanic corrosion needs three things: two dissimilar metals in contact, and a conductive liquid bridging them. You cannot separate the screw from the panel after the fact, but you can eliminate the water. A continuous membrane that fully encapsulates the fastener head, the washer, and the surrounding panel breaks the circuit. The key word is continuous — a coating that terminates at the fastener has done nothing.
Existing Coatings & Condition
My roof already has silver aluminized asphalt coating on it. Do I have to strip it?
Usually not all of it. Remove everything loose, blistered, or delaminating — anything a scraper takes off has to go, because the membrane will only be as attached as what is under it. Over the sound remainder, 7001 Primer both bonds and blocks bleed-through so the asphaltic material does not stain or soften the polyurea. Send photos and we will tell you honestly whether it is a prime-over or a strip.
What if the panels are already pitted or perforated?
Scattered pitting with sound metal around it is a coating candidate — polyurea at 60 mil bridges small perforations readily, and a reinforcing fabric detail handles larger ones. Widespread section loss, panels you can push a screwdriver through, or a deck that is structurally soft is a tear-off. We will say so. We would rather lose a job than warranty a membrane over a substrate that is leaving.
Can it go over an existing acrylic or silicone roof coating?
Acrylic, generally yes with 7001 Primer once the loose material is off and the surface is washed and dry. Silicone is the difficult one — it resists adhesion by design and usually needs to come off or be aggressively abraded and tested. Always run an adhesion test patch on an unknown existing coating before committing the roof.
Does it need recoating on a cycle?
No. That is the practical difference from fibered aluminum and acrylic products, which are maintenance coatings on a repeating schedule. OR-80SLM is a membrane. The aromatic chemistry will chalk cosmetically in UV over time without affecting waterproofing or physical properties; where long-term appearance and peak reflectivity matter, we spec a reflective aliphatic topcoat over it.
Cost, Coverage & Logistics
What is the coverage rate and how do I estimate material?
At 100% solids, one gallon yields 1,604 mil-sq-ft. At a 50-mil aluminum roof spec that is about 32 sq ft per gallon before waste. Add 10–15% for overspray, seam stripe passes, and surface irregularity, and add primer separately. Send us the square footage and we will run the takeoff for you.
How does this compare in cost to replacing the aluminum roof?
A coating restoration typically runs a fraction of tear-off and replacement, and it avoids disposal, structural exposure, and the business interruption of an open building. It also usually qualifies as a maintenance expense rather than a capital project, which matters to some owners more than the material cost does. Against another fibered aluminum recoat, polyurea is more up front and less over ten years.
What equipment does it take to spray?
A plural-component proportioner with heated hose — Graco Reactor E-20 or E-30 class or equivalent. This is not roll-on or airless material. If you do not have a rig, we can refer an applicator in your region, or talk to you about adding the capability including machine selection and training.
Can it be sprayed in cool or humid weather?
Yes, within limits, and better than most alternatives. Pure polyurea is not moisture-sensitive during cure and gels in seconds, so ambient humidity has very little opportunity to affect the film. Substrate temperature and dew point still govern — you cannot coat a panel with condensation on it. We will go over the working window for your climate and season.
Still Have a Question About Your Aluminum Roof?
Ask it directly. Someone who has sprayed aluminum panel will answer — not a call center reading from a brochure.
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