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Dark black oxidised engine casings

Old 05-17-2018, 01:45 PM
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sw74gls
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Default Dark black oxidised engine casings

Hi guys I have spent almost a year now scouring the Internet trying to find an answer to how u can remove severe oxidation from casings I had previously used Gunk ultra on my engines and if you were not more than five minutes it would not corrode or oxidise, however a friend suggested a so called excellent parts cleaner which I was told to pop out and come back five minutes later I did this and I was totally shocked when I came back as it had started foaming the result being it turned nearly black all over !!! Is there anything I can use to bring the casing back to an original cast finish please? ??
if I can find a way I haven't lost a nearly new nineties hanno special 61RF casing plus some of my earlier engines with slight corrosion could be restored I am fingers crossed someone can advise me on this? ? Many thanks Simon.
Old 05-17-2018, 05:02 PM
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The chemicals have "tattooed" the aluminum pores. Almost like an electroless anodizing. Not pretty at all. Too long in the soup, too hot or not enough agitation (or any combination) can cause the stain you describe. The pores are open and absorb the depleted chemical. Normally the aluminum oxide prevents this from happening but while submerged in the chemical etching bath, the oxide is stripped away and the pores laid open.

Soda blasting is probably a good one to try. Do not glass bead or silica blast. The soda (baking soda) is usually quite easy on the surfaces.

BTW, That wonder cleaner was probably laced with sodium hydroxide (lye) In small doses and agitation it can brighten aluminum. Not done right and you now know the rest! Always attend the cleaning. Plenty of brushing about and have plenty of cool clear water on hand!

Some alloys however will darken almost instantly. Alloys with Magnesium seem especially vulnerable . Zing and copper may be as well. Try testing in an inconspicuous area if possible.

Last edited by Jesse Open; 05-17-2018 at 05:08 PM.
Old 05-17-2018, 08:01 PM
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Thank you Jesse for excellent explanation really appreciate it , Cheers Simon.
Old 05-18-2018, 08:58 PM
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Strong akaline cleaners are responsible for the discolored castings.

For cleaning an engine without the ugly oxidation, use Prestone automotive antifreeze heated but not boiling. Keep engine completely submerged at all times. The antifreeze should be diluted 50-50 like you were going to use it in your car.
Add water to the mixture as the level drops to keep the engine submerged or you will have a water mark arou d your casting.
A potpourri pot works best. Takes 24 hrs typically .

Last edited by w8ye; 05-19-2018 at 12:24 PM.
Old 05-18-2018, 09:17 PM
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Originally Posted by sw74gls View Post
Hi guys I have spent almost a year now scouring the Internet trying to find an answer to how u can remove severe oxidation from casings I had previously used Gunk ultra on my engines and if you were not more than five minutes it would not corrode or oxidise, however a friend suggested a so called excellent parts cleaner which I was told to pop out and come back five minutes later I did this and I was totally shocked when I came back as it had started foaming the result being it turned nearly black all over !!! Is there anything I can use to bring the casing back to an original cast finish please? ??
if I can find a way I haven't lost a nearly new nineties hanno special 61RF casing plus some of my earlier engines with slight corrosion could be restored I am fingers crossed someone can advise me on this? ? Many thanks Simon.
I've posted the response below on the diesel forum where you've probably mis-posted your plea.

I'm a volunteer on a warbird restoration. We had the old girl's fuselage "glass bead" blasted to get rid of 75 years worth of paint, corrosion, stains, bird droppings etc. Imagine a spraygun that uses a high pressure stream of tiny particles to clean a surface. Worked marvelously and was remarkably gentle on the Aluminium alloy surface. Environmentally friendly as well.

Hobbyking sell a cheap airbrush "Bead Blaster". I did buy one of them, and tried it with "Soda" ( Sodium Bicarbonate or Baking Soda ) on a sheet of paper with ball point pen notes written on the surface. After a bit of fiddling around with settings I was able to completely remove the writing with little surface damage. That was just a test at the mild end of the range. Such a system should work well on your problem if all else fails. People do bead blast model engines with good results. You can probably tell afterwards that it was "blasted", I can in ebay engine pics. However the results may be much more acceptable than what you have now.

https://hobbyking.com/en_us/single-a...sting-gun.html
Old 05-19-2018, 05:23 AM
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One of the other forums had a thread about this. There was a guy found something that worked well to get the black off. I don't recall the name, but something like Alumibright. I would not worry about it myself. It might be worth more with the black oxide coating?!!!
Old 05-19-2018, 06:00 AM
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Over the last 5 decades I have restored/ rebuilt countless vehicles and their engines.

Glass beads I avoid on alloy engine parts. The beads are glass Made from silica they break down. They open pores in the aluminum and render it prone to stains from oil and fuel. The residual silica dust is abrasive and has no place in an engine.

Glass beads are fine on some structural parts but I do avoid using it on alloy engine parts.
Old 05-19-2018, 06:07 AM
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Originally Posted by Jesse Open View Post
Over the last 5 decades I have restored/ rebuilt countless vehicles and their engines.

Glass beads I avoid on alloy engine parts. The beads are glass Made from silica they break down. They open pores in the aluminum and render it prone to stains from oil and fuel. The residual silica dust is abrasive and has no place in an engine.

Glass beads are fine on some structural parts but I do avoid using it on alloy engine parts.
Our bead sprayer's setup uses water jets in combination with the glass beads. Fine Dry Soda in a special airbrush works just fine on model engine crankcases.
Old 05-20-2018, 08:32 PM
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Originally Posted by qazimoto View Post
I've posted the response below on the diesel forum where you've probably mis-posted your plea.

I'm a volunteer on a warbird restoration. We had the old girl's fuselage "glass bead" blasted to get rid of 75 years worth of paint, corrosion, stains, bird droppings etc. Imagine a spraygun that uses a high pressure stream of tiny particles to clean a surface. Worked marvelously and was remarkably gentle on the Aluminium alloy surface. Environmentally friendly as well.

Hobbyking sell a cheap airbrush "Bead Blaster". I did buy one of them, and tried it with "Soda" ( Sodium Bicarbonate or Baking Soda ) on a sheet of paper with ball point pen notes written on the surface. After a bit of fiddling around with settings I was able to completely remove the writing with little surface damage. That was just a test at the mild end of the range. Such a system should work well on your problem if all else fails. People do bead blast model engines with good results. You can probably tell afterwards that it was "blasted", I can in ebay engine pics. However the results may be much more acceptable than what you have now.

https://hobbyking.com/en_us/single-a...sting-gun.html
Thank you for your kind advice I have followed the link and ordered myself one as you suggested, could you please send me some pics please, also could I pick your brains and ask what kind of soda is used, is it a specific type or not please, Many thanks Simon.
Old 05-21-2018, 01:31 AM
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Originally Posted by sw74gls View Post
Thank you for your kind advice I have followed the link and ordered myself one as you suggested, could you please send me some pics please, also could I pick your brains and ask what kind of soda is used, is it a specific type or not please, Many thanks Simon.
I've answered in your PM but just for completeness the soda is ordinary bicab of soda or baking soda. Also known as Sodium Bicarbonate. Ordinary stuff straight off the supermarket shelves should be fine. Just make sure to crush any lumps into fine powder first. Good luck!

Last edited by qazimoto; 05-21-2018 at 03:54 PM.
Old 05-25-2018, 08:34 PM
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sw74gls
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Hi gazimoto my Bead Blaster came today but unfortunately im unable to connect to my compressor as it has I believe 1/2" Male fitting am I right in saying the hose that comes in the kit is a 3/8" ?? And do I need a 1/2" Female to 3/8" Male ?? Really appreciate all your help so far just eager to have it up and running so I can use it, Thanks you so much Simon.
Old 05-26-2018, 04:33 AM
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FWIW; I got a few engines from a fellow some time ago. Some of them had gotten the “too hot for too long” antifreeze crockpot bath. I couldn’t get them to look like new, but they cleaned up real nicely with some stiff toothbrushes and a paste made from water and Bar Keepers Friend kitchen cleanser. I didn’t take any pictures of the difference it made, but it was significant.
Old 05-31-2018, 06:39 PM
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On the advice of an 'old hand' I tried to shift some stubborn aged castor varnish from a FUJI .15 IV case by boiling on water for 15 minutes.

No detergent or degreaser added.

The baked-on varnish loosened, but I was disappointed to see that the case had darkened appreciably.

I believe a warm (not hot) two hour crock pot bath with 50:50 water/ full strength 'green' anti freeze is a better option for clean up.

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