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Aluminium composite questions
hi again,
Another question from the planning conservation man about the materials used for the flat cut lettering, they are happy with a brushed gold 3mm letter, but they want to know the following :-
"The 2-3mm sandwich material put forward by the sign company does seem to be a suitable overall thickness. The concerns relate to the detail quality and durability of the material. Could you please obtain from the sign company the precise nature of the material they are proposing on the front face of the letters, ie brushed or anodised aluminium; and whether it has any sort of surface coating to the face. Looking at the samples on site the edges did look particularly vulnerable and it was possible to imagine that over time corrosion would occur and grow around the edges of all of the cut out letters. It is believed that it is necessary to both seal the edges and to colour them so that none of the plastic core is visible."
This is what he is asking, but I am a bit unsure how to answer that. An overall lacquer, accorind to dibond website would not have inferior adhesion to the cut edges.
I think they are being very picky. I havent had to deal with a conservation officer before :S
Please help if you can
Thanks
Matt
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13 Replies
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Matt, can’t you use 3mm brushed gold acrylic i think there is such a product so a perfect edge (?)
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really, i didnt know that, no chance you know where i can get that at all??
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call perspex distribution and ask for a pearlescent caramel gold 5PYO sample
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thanks george, ill give it a whirl.
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i also would mention that this material is used externally as a building material throughout the world.
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are you referring to dibond dave?
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quote Matt Hards:Another question from the planning conservation man about the materials used for the flat cut lettering, they are happy with a brushed gold 3mm letter, but they want to know the following :-“The 2-3mm sandwich material put forward by the sign company does seem to be a suitable overall thickness. The concerns relate to the detail quality and durability of the material. Could you please obtain from the sign company the precise nature of the material they are proposing on the front face of the letters, ie brushed or anodised aluminium; and whether it has any sort of surface coating to the face. Looking at the samples on site the edges did look particularly vulnerable and it was possible to imagine that over time corrosion would occur and grow around the edges of all of the cut out letters. It is believed that it is necessary to both seal the edges and to colour them so that none of the plastic core is visible.”
He’s wrong
Dibond is an aluminium/polyethylene composite material. Aluminium does not rust in the way he understands which is why it’s an ideal choice for this type of application.
What a jerk. 🙄
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The only down side to aluminium is its not very good in a marine/salty environment but you should still get 10-15 years out of it before problems occur. The metal slowly turns to powder and the top surface will blister and flake. It will only happen on untreated aluminium and would propogate over the surface.
In a Phrase………"Absolutely no problem with this material" (and I did metallurgy as part of my engineering career!!!)
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I disagree, I’ve seen these letters degrade in less than 12 months on a sea front, I now acrylic laquer them before fitting which has solved the problem.
Also, if your supplier uses simplefix locators you will be back in 3 years to change the cups, what a pain!, I use only snapfix as they have a lifetime guarantee on the cups, always worth checking with whoever you get you letters from what locators they use.
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quote gordgeko:I disagree, I’ve seen these letters degrade in less than 12 months on a sea front, I now acrylic laquer them before fitting which has solved the problem.
I am somewhat puzzled by your experience Gordgeko.
My understanding is that aluminium resists corrosion because it forms a very thin aluminium oxide coating which resists any further corrosion of the metal. However, if Aluminium is in contact with some other metal (e.g a screw fixing) then an electrolytic reaction will take place between the two metals causing one of the metals to degrade. Could your experience of the short life of composite material be explained by a "metal to metal" reaction rather than (as you have assumed) atmospheric corrosion?
I recently replaced a full set of flat cut butler dibond lettering on a shop fascia (it had been up for three years) and can reliably report that there was no sign of any "corrosion" of the type feared by the planning official at the start of this thread. Admittedly, this was not in an area close to the sea.
I fail to see how the planning official expects the edges of the lettering to be effectively sealed and painted unless the whole flat cut letter is to be painted. The planning officials suggestion is both impractical and unnecessary.
I agree completely about the choice of locators though. Certain types of nylon locators do quickly degrade and become very brittle leading to failure, however, the planning official has not expressed any concern of this type being more concerned about something he "imagines" might happen rather than expressing any reliably informed opinions (Hence my distaste for local government officialdom).
As with all projects – budgets come into play, and there is no point in over engineering something if there is no practical benefit, as this will only add to the cost.
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The rate of corrosion will depend on the quality of the aluminium, I’ve seen Japanese bike parts corrode badly within months of contact with road salt.
I’d use acrylic or edge seal the composite.Steve
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how would you edge seal it though, shall i just go to halfords and buy a clear lacquer spray and just spray the edges??
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Matt If I were in your situation, I’d be contacting the manufacturers of the composite board to see what their thoughts were on the matter.
They should have all the information you need regarding the possibility’s of edge corrosion and whether its going to be an issue or not. If its happened in the past they will know about it, after all tons of the stuff is machined and installed each year.
I’m not 100% sure on the manufacturing process but is it not possible they apply an anodised coating to the inside of the sheet before laminating polyethylene core.Another issue you may have if you tried to seal the edge is getting it to stick. .. not much surface area of aluminum, and not much sticks to polyethylene.
Anyway best of luck and let us know the results !
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