Why are my aluminium window frames crumbling?

[Jules2023]

 

 

 

About 6 weeks ago I was window cleaning and noticed some soft spots in my coated aluminium window frames, which appeared to be crumbling and some clear silicone looking substance behind. Since then it has dried and shrunk and can see right through to the wall cavity. House (and assuming windows) is about 27yo, this window is on exposed wnw wall, but have the same thing on a sliding door frame on sheltered opposite side of house.

Has anyone seen this? I read about how mortar can react with aluminium, and the damage is certainly in line with mortar joints. Any recommendation for a fix? I'm guessing at least some expanding foam?

[Jason]

Oh dear @Jules2023, sorry to read of the damage to your windows. I hope Workshop community members will be able to suggest some remedies other than replacing them.

Let me tag some helpful members to kick off the discussion: @EricL, @Jewelleryrescue, @tom_builds, @TedBear and @Marty_greenshed.

Jason

[MikeTNZ]

Hi @Jules2023,

Yes, I have the same sort of aluminium windows and sort of the same bricks (just a different colour).

Like yourself, I was washing my windows and noticed this sort of "damage", if you can call it that.

What this is, is galvanic corrosion, aluminium is a terrible metal when it is in contact with other chemicals, it is extremely reactive,

hence the degradation of the parent metal.

What I did, was sourced some nitric acid (extremely dilute) from an industrial chemical provider here and washed all of my window frames down with a toothbrush and the solution, if you are going to do this wear decent dishwashing gloves.

I also water-blasted the bricks around the windows, because there is always a chance that there are salts coming out of the bricks, years after they were laid.

After everything had dried, I ran a bead of neutral cure RTV silicone sealant under the edges of the aluminium sections and the bits that had become compromised, I have had no further issues with degradation.

[EricL]

Hello @Jules2023 

Great minds think alike! I was going to suggest self-expanding foam to fill up the cavity inside the aluminium channel. It should also be able to keep up with any movement or temperature changes the window might experience. I only suggest using a primer on the surface of the foam before you paint it with your topcoat. 

Another product I would like to suggest is Turbo 175ml Builders Bog Flexipack. It can be shaped and sanded down, plus it can be painted over once it has fully cured.

Let me call on our experienced members @Dave-1 and @robchin for their recommendations.

If you need further assistance, please let us know.

Eric

[robchin]

@MikeTNZ @EricL - I reckon you are spot on there. The use of neutral cure silicon is the key here. The holes are neatly aligned with the mortar in between the bricks which make sense with the chemical reactions going on. 

Good luck @Jules2023 

[Dave-1]

Afternoon @Jules2023 

Oh man.... Thats something I have not seen before, Ive seen aluminum corode as in looking like puffed rust but not this.

I really like @MikeTNZ 's information, something to file away and keep in mind for sure.

@EricL's suggestion matches with what I had in mind to bring it back to being secure from wind and rain. Id use his steps especiallythe builders bog after neautralising as Mike suggested. 

Id be making a calander appointment for doing a walk around once a year and having a look just to keep in check. I seriously thought "has someone been punching holes in the framing?" lol Tho that round hole has me thinking maybe pressure test with your fingers the whole way around all of your windows. 

Dave

[MikeTNZ]

Hi @EricL,

Personally, I would probably be quite hesitant to use something like expanding foam, I don't really know the chemical

composition of that stuff and that could cause further issues down the track.

Also, expanding foam, when it cures, turns quite hard, that is why I used a neutral cure (don't use acid cure with aluminium)

Silicone sealant, because that remains flexible to a degree after it has cured

Bear in mind that aluminium does not like other chemicals around it, it's nice and soft, lightweight and easy to work with,

but it does have the downfall that it will react with other chemicals and especially other metals (copper is one of the worst).

[EricL]

Hi @MikeTNZ 

Thanks for sharing your concern. Just to be on the safe side I'll get in touch with our supplier and try to get more information regarding the use of expanding foam on aluminium.

Eric

[EricL]

Hello @MikeTNZ 

My apologies for the late reply. I've spoken to Polyfilla's technical team, and they said that its perfectly alright to use self-expanding foam on aluminium. The only effect mentioned is that it will stick to the aluminium walls but that's about all it will do.

Eric

[Jules2023]

Thank you all for your responses. I unfortunately haven't found time to address this but hoping to soon. 
couple of follow up questions:

- can I get away without using the nitric acid wash that was suggested? ie if I put in the silicone/foam fill and bead, wouldn't the reaction stop?

- how do I get a bead of silicone between the frame and bricks if the fit is very tight? There isn't space to get a normal applicator in there - maybe 1mm only for much of it. 

thanks again