Dealing with aluminium corrosion

[Rivertest]

I’m currently restoring an old Russian Tal 2 telescope circa 1996. It’s been stored for a number of years in its original wooden packing case in a shed. Half of main tube was suffering from raised and flaky paint work, which when easily scrapped off revealed a grey thick dust which was obviously corrosion. I’ve now fully stripped it and as you can see where the corrosion has been removed it is still discoloured so was wondering if it needs neutralising before being etch primed. Has anyone got any pointers please. Thanks all.

 

[voipio]

That blue is definitely not the Tal 2 original colour, which was a sort of pale grey. What's the state of the primary mirror?

 

[Rivertest]

That blue is definitely not the Tal 2 original colour, which was a sort of pale grey. What's the state of the primary mirror?

Hi Voipio, in my travels around the inter webs I've seen a few lovely blue Tal's and as you say, they also came in grey and of course white. Plan is to 'film wrap' mine which will make it a bit more durable while banging it around setting it up , only kidding. Surprisingly the mirrors are both good thankyou I used it for a bit as I needed to get the clock drive working and make sure it was all in order before refurbing. I'm currently on the hunt for some Tal specific Barlow eyepieces, the 32mm not 1.25”. If you hear of anything Tal……..

 

[Ross365]

I've had really good results on badly corroded Al using Hammerite Speciality Metal Primer. These days, I'm not a big fan of Hammerite except for this product. Unfortunately, it only comes as brush-on paint (it's water-based) so it's hard to get the finish you could with spray.

Otherwise, will that surface improve with fine sanding or even a wire brush on a drill?

 

[500e]

Alumiprep then Alodine

 

[RWD3M]

Or this:

Alocrom 1200 - Aluminium Surface Engineering

Alocrom 1200 provides a cost effective protective iridescent gold coating, with particularly excellent corrosion resistance properties.

ase4anodising.co.uk

Which is what we used in the structures bay in my former life.

 

[500e]

Both Alocrom and Alodine put on chromate conversion coating that protects metals, most typically aluminum, from corrosion.
The Alumiprep Sudal is a cleaner inhibitor
Read the H&S sheets.

 

[Rivertest]

#Ross365, yes I did consider about the wire brush but I think that may be touch aggressive. I read last night on the inter webs that diluted white vinegar is a good ali cleaner. So a washed down with thinners, then gave it a good scrub with green scotch Brite and G101, then coated it with the vinegar solution for an hour keeping it wet, washed it off with more G101 and rinsed with clean water. The corroded areas are know the same colour as the rest of the tube so I believe that should sort it. Just need to mask up, panel clean it and on with etch primer

PS. Sorry just seen your replies 500e and RWD3M. Will look into these products also, although I believe this stuff is considered pretty unhealthy these day so you have to send stuff out to a specialist.

 

[500e]

Aircraft Spruce stock I think or the new formulation

 

[Pigeon_Droppings2]

I'd use an aluminium specific primer...I made the mistake of using regular etch primer and it just peeled off after I put the top coat on. Luckily I was just painting gutters....second time around I bought the right primer and it's worked.

I used a universal etch primer for difficult surfaces (Jenolite).

 

[Rivertest]

Great advice PD, I was going to use UPOL etch primer that I had hanging about and just checked the spec. It’s for steel.

POWER CAN Etch Primer

Use for priming bare metal surfaces to promote adhesion of paint and prevent the metal surface from rusting.

www.u-pol.com

I need to use this type for ali

ACID#8 1K Acid Etch Primer

Promotes paint adhesion to difficult substrates such as galvanised steel and aluminium. Ideal for rub through areas in primer prior to application of colour.

www.u-pol.com

Thanks again, that saved me a whole lot of trouble.

RT

 

[Pigeon_Droppings2]

I was going to use UPOL etch primer that I had hanging about and just checked the spec. It’s for steel

Thats exactly what I did (same UPOL stuff I use on steel)...I figured etch primer is etch primer....boy was I annoyed.

Had to strip them all back and start again....the Jenolite stuff did the trick...gutters have been outside over the winter and no sign of anything flaking. I also looked at the upol offering but seem to remember it was a bit expensive?