Aluminum Alloy aging

[nz2]

The aluminum radiator tanks and side panels on some of our trucks ( 1920's and earlier) need replacing. Looking at getting replacement aluminum sections cast or fabricated up, but either way the finish is too polished and bright, and does not match existing sections. It would be nice to have that aged look to the whole radiator unit.

Any ideas as to methods in oxidizing new alloy to make it look old? Caustic soda or similar?

I realize this goes against the general trend of polishing an item up and being shiny so it looks good, but I want the image of a light grey finish.

Doug

[Paul Drake]

Definitely not caustic soda. I left some steel nuts and bolts in an aluminium tray, in a caustic soda degreaser. After an hour, the tray was gone! That was before I knew better. I don't know if it would give the desired effect for a shorter timescale.

[ferrettkitt]

I've used caustic soda for stripping paint off items it works a treat on steel but aluminium has to be watched other wise it will erode away (already mentioned). Some aluminium depending on its grade will last longer than say an item that has been cast rather then formed out of sheets.

[G506]

On stainless steel I have used bead blasting to dull down the finish, which worked superbly. I've used the same principle with alloy, but great care obviously needs to be taken due to the material being softer

[robin craig]

You have actually asked two questions here.

 

Aluminium acquires an oxide layer very quickly, in fact 20 minutes and it is happening, why do I know? I weld the stuff. Mechanical cleaning is always best prior to welding and not the week before but right there and then.

 

As far as an age acquired patina thats down to your own methods.

 

Robin

[Rover8FFR]

I believe that Coke Cola has an effect or making metals patinate rapidly.

 

I believe that the VW boys splash it all over the Bugs and Campers to get that rusty old exposed steel look.

 

As with anything try on a spare piece first.

 

It may work and it may not but worth a try and you can drink the liquid if all else fails. :cool2:

[Pzkpfw-e]

Aluminium is a highly reactive metal, hence the immediate formation of an oxide layer on exposure to air. Dipping it and steel into Sodium Hydroxide causes and battery effect (As I remember from my youth, putting a pencil sharpener, alloy body, steel blade into the stuff. The alloy corrodes very rapidly, with bubbles of Hydrogen coming off)

I don't know if cola works these days, it used to contain Phosphoric acid (hence the ability to shine up old pennies!).

[Tony B]

If you've ever seen how Coke is made, the last thing you'd do is drink it! :red:

[The Bedford Boys]

What about if you bead blasted it?

[ferrettkitt]

I was looking through one of the catalogues that the missus gets it was selling a picture of a Spitfire with a piece of real Spitfire. The alloy had aged due to it being underground (acidic soil) would that be an option for ageing the material? Don't jump to hard on me just thinking in and around the box.

[plainmilitary]

Some of our clients in the car restoration game always ask us for the old alloy look on there steering wheels. What we do is use a very fine wire wool for a brushed Alloy look. The finer the wool the better and if you don't like the look, it's easy to polish out again.

Tony.

[nz2]

So many options to date. It will be a trial time with different chemicals being tried. I am surprised to date that no one has come up with a direct comment as "been there , done that."

Thanks to all

Doug:cheesy:

[G506]

What about if you bead blasted it?

 

Suggest you have a look at post number 4............

[Tony B]

What about vinegar? I've seen that used to artifically age metal. Boil and paint on while hot. The Non Brewed Condiment variety is the choice.

[nz2]

Suggest you have a look at post number 4........

 

I was not trying to be disrespectful to individuals and their suggestions. All offers are gratefully acknowledged, and different approaches to be tried.

In talking to local vintage people it's also been suggested using citric acid, by rubbing a lemon over the surface. Salty water was another. I think that was more in line for steel work.

 

Time to try and report

Doug

[stalwart]

If you just leave it out in the weather or a damp garage it will all too quickly oxidise and dull. Some times the simple solutions are the best .

David

[nz2]

Another suggestion today from an industrial chemist was to wave a gas flame over it, to encourage oxidation. She was thinking of the teaching process of heating copper to produce copper oxides.

Another engineer could not think of directly a simple process to discolour the alloy, being otherwise accustomed to polished material for his branch of the trade.

He did however note that lanolin was used on the surfaces of alloys to retain the sheen.From that we worked backwards to the realization that steel and cast objects out in a paddock with sheep about, do not rust about the rubbed areas due to the lanolin from the wool. That worn, glossy state for unpainted steel objects can be obtain using raw wool!

Doug:cheesy:

[plainmilitary]

Lanolain must work, I've never seen a rusty lamb lol.

[nz2]

Now I have my own computer back and operating I've located a photo of one of the radiators to be rebuilt. This is from a 1921 model Leyland with differing mounts to the RAF style of radiator.

In common with so many radiators of the period its the top and bottom tanks which corrode and need to be rebuilt. This image does show the colour of the side panels I wish to re create.

Doug:-\

[robin craig]

I would say that the hot to cold and back to hot cycling that went on is partly to blame for the degradation and also possibly from the inside out considering the ditch water concoction contained within.

 

Also add to that the work hardening of the material, in all no surprise to me

 

R