My sanded brass inlays have turned white/silver

[sams93]

I have been making a project where I have set into some walnut some brass inlays. They started off as a single 1m long 1cm wide 2mm thick strip of brass, and then I cut them down with the bandsaw lengthways to give me a 1m long 0.5cm wide piece, then in half again to give me 4 pieces of 50cm x 0.5cm x 0.2cm of brass.

I set them into the piece leaving them slightly proud by maybe 0.5mm, as I planned to sand them to flush later.

They started off as a nice yellow colour, but after sanding they have turned to a bright white/silver colour.

It isn't the end of the world, but I wondered how I would get them back to the yellow colour they started. I sanded up to 600 grit.

 

[PerryGunn]

The white will be oxidation of the brass, if you re-sand (or use wire wool) it'll disappear for a while then come back because the metal surface is exposed to the air.

To prevent it you need to seal the metal - wax will work but needs fairly frequent application, a clear lacquer will last longer

 

[Phill05]

Are they just dipped brass or solid? they could have been coated and you wiped it off.

 

[sams93]

Are they just dipped brass or solid? they could have been coated and you wiped it off.

That is a v good point. As far as I was aware they were solid brass.

It was this
https://www.diy.com/departments/brass-flat-bar-l-1000mm-w-10mm-t-2mm/254115_BQ.prd

 

[Phill05]

Well it say's solid brass on the advert, when you make a saw cut through it can you see the bright brass colour or the white with a yellow coating round the edge.

I have worked with a lot of brass and never seen it go white naturally.

 

[sams93]

It is solid brass, maybe it’s just brighter than I was expecting after sanding, it’s a real yellow in those pieces but on my piece it’s much brighter almost chromed

 

[Old.bodger]

Can you do a picture if the problem piece?

 

[Droogs]

If they are solid brass, then it is down to 2 reasons. The first is that you have polished the surface with finer and finer grit making the surface more reflective and have also reduced the surface area you sea and therefore, you see less of the metal's colour and more of the reflected light.

 

[PerryGunn]

Here's an example of white corrosion on brass

I am not a metallurgist but, as I understand the process, brass is an alloy of Copper and Zinc and, depending on the composition of the brass, exposure to air can produce a thin surface layer of zinc oxide (which is white).

 

[sams93]

If they are solid brass, then it is down to 2 reasons. The first is that you have polished the surface with finer and finer grit making the surface more reflective and have also reduced the surface area you sea and therefore, you see less of the metal's colour and more of the reflected light.

I think this is what has happened - It still had a slightly yellow tinge but was really reflective and so looked very bright and silvery. I have noticed that even over the past 24h since I did it that it has become more yellow in this short space of time, so I wonder if it will continue to yellow further over the next couple of days.

 

[sams93]

Can you do a picture if the problem piece?

It isn't really a problem and I am actually really happy with how it has come out overall, just isn't quite the colour I was expecting from the metal I had started with

't

 

[PerryGunn]

I don't think that's white - it just looks like diffuse reflection from the surface caused by the fine scratch lines left by the sanding. Perhaps you need to go through a couple of finer grades of sanding to produce a smoother surface and possibly finish with wire wool followed by a metal polish (I've never tried sanding brass so I don't know how fine you need to go)

 

[sams93]

 

[Fergie 307]

I would agree with the last, 600 grit is actually quite coarse. Try something like 1500 or 2000 on one of your leftover bits and see what happens. I know on old rolled gold items, basically a sandwich of two thin layers of gold either side of a piece of brass, when the surface gold later wears away and you polish it up before plating it's hard to tell where the brass ends and the gold behind as it comes up such a rich yellow.

 

[Iestynd]

Lovely work mind you on that chess board. It looks brilliant

 

[sams93]

Lovely work mind you on that chess board. It looks brilliant

Thanks!

 

[markparkinson998]

Are they just dipped brass or solid? they could have been coated and you wiped it off.

I would agree with you, as I have worked a lot with both wood and metals, if you cut or sand it should not change colour unless it is merely plated.

 

[mikej460]

A long time back I polished the solid brass lever cap on my LN block plane using autosol (I know.. I know..) and it polished to an incredibly bright whitish colour but soon returned to a decent patina.

 

[user 35906]

Unprotected brass soon dulls with age but is easy to brighten up with light abrasion. If it's to bright at the moment rub it with your fingers to tarnish it.
In an earlier life I used to clean old ship wreck port holes in acid and then finish them off a wire brush and lacquer them to keep them bright for wall mounting.
If you check with a magnet you will soon see if it's only brass plated.

 

[Phill05]

Here's an example of white corrosion on brass
View attachment 136047

I am not a metallurgist but, as I understand the process, brass is an alloy of Copper and Zinc and, depending on the composition of the brass, exposure to air can produce a thin surface layer of zinc oxide (which is white).

I totally agree with you but and this is a big BUT your casing have years of neglect to get to that stage, the brass in question was new brass and clean cut and in all the brass I have in stock I have never seen that kind of corrosion.

Anyway looks like the problem has been solved and a fine chess board it has turned out to be well done sam93.