my polished alloy has a gold metalic look to it

[daz2206]

Hello.... this is my first post on the forum and im new to polishing, ive been polishing my car engine covers but some parts have a gold metalic look to them after being polished. ive spent at least 100 hours on it so far as i made the mistake of starting with 80 grit wet/dry sandpaper (if id used paint stripper first i would have seen that the alloy was already smooth under the mottled effect paint but i know for the future lol) im learning quite a bit from the forum and think im slowly getting there, ive used the search but i cant seem to find anyone else having this problem (maybe nissan skylines use cheap alloy ?) here is a pic of my engine and you can see at the front (cambelt cover) what i mean, its worse when the sun shines on it but its still noticeable whatever light shines on it, any help would be much appreciated. (i apologize for the size of the pic, i dont know how to make it smaller)

[mpierich]

Looks pretty good to me - I can't really see any gold color on my monitor. Unless you're "burning" the material during polishing, I don't think there's anything to be done about color variations. Of course if it bothers you much you could always anodize it all dayglo pink or something...

[grommit]

looks like for a beginner like me you are gaining the experience and knowledge passed on by all the helpers on this site, my friend has the same problem with his skyline and all i can think of is heat, i have done quite a bit on his car for him(rectifying his ?!*£ ups!!) he is happy with the results, but if i were you i would consider mpierich's suggestion as you know it will only work on your mind, as by the picture you are a guy who strides for perfection in your car...it took me aprox a year of getting help of the guys experimenting etc and learning by mistakes etc befor i got confident to do jobs on expensive parts or for other people,so you have done well.
take care,
Grommit

[daz2206]

thank you for the replies, if ive burnt it, is it possible to start over or will it be like this right through the alloy ? il take a very close up pic tomorrow and hopefully someone might be able to tell better where ive gone wrong.

[mpierich]

Originally Posted by daz2206

thank you for the replies, if ive burnt it, is it possible to start over or will it be like this right through the alloy ? il take a very close up pic tomorrow and hopefully someone might be able to tell better where ive gone wrong.

Maybe try taking a small section of the yellow part back, starting with 320-grit or so, then working back up to a polished surface (being careful not to overdo it on the speed and pressure) and see if there's any difference. If you did "burn" it, it should only be on the surface.

[twinturbo_rotary]

in your picture it looks really good, did it turn yellow after time or was it like that when you polished it?

the rb26 is cool engine what model is your car R33 -R34 ?

[daz2206]

it turned gold metallicy looking as i was polishing it, its an r32 gtr (1994)

[twinturbo_rotary]

R32 nice, i think there is no way to get the yellow tint off, when i took cast aluminum engine parts to my friends shop to get tig welded he told me that it might not look as good as it could because the cast aluminum absorbs oil and its hard to get out, so i'm thinking that the yellow gold color on your valve cover is just is from oil.

[daz2206]

thanks for the help, i have loads and loads of skyline bits to polish so il have another go and see how they turn out, i think im getting a little better at polishing since i did my own covers (thanks to the guys on this forum) so hopefully the next bits will come out better than the ones in the pics.

[mojoe]

Originally Posted by twinturbo_rotary

R32 nice, i think there is no way to get the yellow tint off, when i took cast aluminum engine parts to my friends shop to get tig welded he told me that it might not look as good as it could because the cast aluminum absorbs oil and its hard to get out, so i'm thinking that the yellow gold color on your valve cover is just is from oil.

I can see aluminum absorbing oil over time.
Just a thought that popped into my head......what about heating the part in an oven?
you know....like prepping for powdercoating in order to get the contaminates out of it. think that might work? maybe as it cools down a bit so as not to shoot off too much smoke, spray it down with some acetone or carb cleaner. then give it a good cleaning before starting the polishing process.