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Alstone · Moderator & Site Supporter

The problem with mending altering or modifying anything is having the right tools and equipment, but the things you require are either expensive or unobtainable where you live, so I thought I would do a few guides on different aspects of engineering practice, using what is available generally, also things that are orientated towards airguns.

The first is to do with colouring of metals.

First it is very important that all metal objects for chemical colouring are clean. The object should be polished . Then it should be de-greased with methylated spirit or some other grease solvent, and if possible finally dip into a bath of warm dilute hydrochloric acid (spirits of salts) for a minute or two, then rinse in warm water.

A Dead-Black Surface
Most common metal can be given a black surface coloration by using chemicals, Brass and Copper can be blackened by immersion for a few minutes in the following liquid:
(Brass)
Copper nitrate . . . 1oz
Water . . . 3oz

Copper objects can acquire a slightly shiny black surface by immersion in the following solution:
(Copper)
Ammonium sulphite (liver of sulphur) 1 part
Water 4 parts

If you immerse brass in the above they will come out a steely gray colour.
Another way of colouring brass or copper ending in black is, immersing in a very dilute solution of Ammonium or sodium sulphide. In a very weak solution brass will take on a golden appearance, and copper will be reddened, by making the solution stronger or leaving the object in longer the colour can be obtained from yellow, red brown or black.

Iron objects can be coloured by immersing in a solution of photographers “Hypo,” they are given a blue-black colour, particularly if a little lead acetate or nitrate is dissolved in the hypo.
A pleasant gray colour can be produced on Iron by boiling it for half an hour in a weak solution of iron phosphate.

Aluminium can be dulled by immersing in a hot moderately strong solution of caustic soda (sodium hydroxide) for a few seconds. The metal will thereafter have a matt appearance. If the object just treated is immediately rinsed in warm water the immersed in a hot solution of an aniline dye (clothes dye)the aluminium surface will take up some of the dye and become permanently tinted.

Have fun.

Al

swl · Member

Al
Can you tell me how I can renew a dark brown finnish on aluminium.
Somehow I abraded one of my Hardy fishing reels and now I have patches of bare metal.
Regards.
swl

Alstone · Moderator & Site Supporter

Hi swl

The reel will more than likely be anodised, and bald patches cannot be repaired, you will have to strip the reel back to bare aluminium then re anodise it.

or send it to a commercial plating house. Personally for something like a fishing reel I would do that, it would stand up to the wear and tear better.
The other options you have are to have ago yourself (see above), or anodise it using a electrolysis process which is difficult.
If you do have a go at doing it yourself then you can use a Dylon clothes dye or ink as used in you printer.

The only other way you might repair the patches is to use a paint on aluminium dye, the only problem with that is the only colour you can get is black.

Al

kanyon · Silver Status Member

Aluminium can be dulled by immersing in a hot moderately strong solution of caustic soda (sodium hydroxide) for a few seconds. The metal will thereafter have a matt appearance. If the object just treated is immediately rinsed in warm water the immersed in a hot solution of an aniline dye (clothes dye)the aluminium surface will take up some of the dye and become permanently tinted.

Have fun.

Al[/quote]
Hi Al.....How well dose the alloy colouring work?
Is the colour dark/light or dose it depend on the time in the dye?
Dose the caustic soda remove the oxadised layer then return
while in the dye getting coloured at the same time.

Anyways I will most surely give it a try.
Got to be the easyest way I have heard so far Smile

Alstone · Moderator & Site Supporter

Hi Kanyon
The aluminium will have a permanent matt finish after removing from the caustic soda, if you go on to colouring the object the degree of depth of the tint will depend on the type of dye used, also the length of time in the dye but no more than half an hour should be ok, also make sure the dye solution is warm. you will not get a deep colour finish more like a deep tint, but in red, green, brown etc it looks good and it will be permanent.

All these methods of colouring are what were used many years ago and the above is a basic system of anodizing, so probably not as good as a commercial product but cheaper to do and easier.

The thing is to do a test piece first and change dye's, time in the bath etc.

Al

cw · Banned

Liver of sulpher? Now that's English!

Alstone · Moderator & Site Supporter

We try to cater for all types CW. Smile

Al