Norma,
Thank you for posting this picture. We need to see more pictures of ACM failures, because we are using the hell out of this product.
ACM is a beautiful thing. A game-changer, really, when you compare it to the old labor-intensive MDO plywood. And the way the panel is installed in the picture might work, Norma, if the material were something more substantial. If I were making a panel like this for a customer and I knew they were going to install it like this, I would have used .080" aluminum, preferably with a back frame of square aluminum tube or 1/4-thick aluminum angle. This would accomplish two things. It would not warp at all. But also, it would be so heavy that the installer would be forced to use some substantial method for fastening it to the building. He would be scared not to.
ACM, especially the cheaper 5-year versions we are using now, is going to see more failures, I believe, as time goes by. I am seeing delaminations now, so I would not use ACM for a routered face of a lighted sign. This type of routered sign is expensive to build and going cheap on the routered face may backfire. "Best practice," in my opinion, calls for .080" aluminum for routered faces, backed by 3/16" acrylic mounted with welded studs and finger-tight nuts. A routered face of ACM backed with thin acrylic mounted with double-sided tape may be likely to fail. Either the ACM will begin to delaminate or the plastic backer will fall off inside. This type of sign is expensive to build, so why cheap-out on the face?
I want to add that, in contrast to the ACM panels the industry started using years ago, the ACM panels now are of lesser quality. I remember some ACM brands that carried a 15-year warranty at one time. Do any of them now? Most seem to be rated at five years—hell, that's the rating for MDO. Some brands are even "five-year limited." Limited? What the heck does that mean? I asked a manufacturer rep once about that and he said, "we want you to use an edge cap on ACM." Good grief, does that not defeat the purpose?
An ACM panel is only as good as its adhesive and its paint job. Now that there are many players manufacturing it, who knows what we are getting and what we are using? The price of this stuff is a fraction of what it was when it first came on the market. Do I not remember pricing of over 200 dollars a sheet many years ago? Or is my memory totally failing?
ACM has been around for a long time. It has been used by the construction industry for many years on storefronts. Numerous auto dealerships with their fancy fronts use ACM extensively. But I believe the quality has plummeted. Was the aluminum skin always so paper thin? It is typically 12, 11, or even 10 mils (not millimeters, but mils) in thickness. That translates to .020", .011", and .010". That's getting close to some vinyl thicknesses. Has it always been so thin?
One problem, when the aluminum skin is so thin, is that it can easily corrode all the way through if in contact with a metal that galvanically reacts to it (like stainless steel). I have seen ACM skins get eaten away around a fastener from contact with stainless steel screws (in the presence of moisture). The galvanic reaction between aluminum and stainless steel has never been a big issue in sign work in the past because we have typically used much greater thicknesses of aluminum. Engineers have routinely required insulating washers (nylon, for example) between these two metals in some areas of construction (hanging HVAC equipment from ceilings in indoor pools, for example). We in the sign industry have never really been bothered by this incompatibility between stainless and aluminum—but we have never used paper-thin aluminum till recent years. And honestly, many of us sign goobers are so cheap that we ignore stainless steel fasteners, anyway. Interestingly, one metals guy who claimed to be an authority told me that, for installing ACM panels, I should use aluminum fasteners, or galvanized screws as a second choice.
And what are they painting the ACM aluminum skins with? I can't believe that our stuff gets painted with anything as durable as PVDF. Hopefully, it's polyurethane. But if many of the sign panel brands are using the cheap old polyester coatings like aluminum from years ago, I won't be surprised. All these aluminum skins are painted by "coil-coating," which is a method of roller-coating using machines as big as a warehouse. It is high production and they have one goal in mind—produce a low-cost product.
And though we may be quick to blame the Chinese, they only do what buyers tell them to do. If a US buyer says "make it cheap," the Chinese say, "no problem." Big coil-coating operations are not just in China, but in India, Mexico, and other places as well.
End of rant.
I should ride my bike tomorrow. It helps when I'm feeling frustrated.
Have a nice day.
Brad in Kansas City
