Cleaning magnesium?? - turning into the black paint debate

Andy · 2003-03-24T03:58:54+00:00

So what does everyone use to clean type 1 cases and gear boxes?? I've been soaking an old gear box with kero for a week, then for a day with degreaser before pressure cleaning. All the junk is off, but it still looks dirty. Even scrubbing with a stiff brush doesn't seem to do the job. I have seen some acid based aluminium cleaners, but are they a little violent for magnesium, and will the remove baked in dirt?? Thanks, Andy [Edited on 25-3-2003 by Baja Wes]

PatB Casual Dubber

32 posts · joined Mar 2003 · 27 Mar 2003, 10:19 pm

#34540

Although I'm a newcomer to VWs I've spent quite a few years playing with air cooled motorcycles. In the days when air cooling (free air rather than forced of course) reigned supreme, even on the highest output four stroke engines and hyper stressed two stroke screamers, manufacturers applied a variety of finishes to their engines from satin black, through dull, lacquered alloy to polished alloy. Some engines received different finishes depending of the style of bike they were fitted in whilst remaining identical from an engineering point of view. I can't think of a single case of a bike engine dying as a direct result of general overheating (as opposed to holing a piston due to lean mixture or similar).

Even before I became aware of the great VW paint/no paint debate I'd started to suspect that, as long as an engine is in good nick and not severely abused, with an intact cooling system the differences wouldn't be great.

Would I paint my engine? Yep, but that's because I grew up where road salt will dissolve magnesium alloy before your very eyes and old habits die hard.

70AutoStik Insano Dub Head

730 posts · joined Aug 2002 · 27 Mar 2003, 10:21 pm

#34543

Wes, I had a friend who had the fins of his 45 chromed, with black-anodised heads (Harleys are air-cooled, too; remember) and it looked fantastic and ran well (the rocker covers were re-chromed, too.) I think he later painted the primary cover gloss red - this is more than 20 years ago!

Yes, "forced convection" is the correct engineering term, but think about it - the heat is still conducted to the air. Chrome plating is so thin it makes bugger all difference to the texture of the surface - even "triple chrome." I, personally, don't like painted cases- but I love things looking really "mechanical." A painted case (if done right) should work OK, but paint on the cooling fins of the cylinders or heads (possibly the sump) is likely to cause problems. But try not to be such a fresh engineering graduate - plating or anodising the cooling areas is not likely to cause any great problems.

I will add as a postscript that there are paints that can be used in such areas, but as inferior products also make such claims, I won't recommend any.

Baja Wes V6 Baja Pioneer

3,119 posts · joined Aug 2002 · 27 Mar 2003, 10:25 pm

#34547

Exactly what I'm saying, paint colour has very little effect. Although I have never seen a factory motorcycle with chrome plated fins before, and don't think it would be a good idea.

Motorcycles also use a much wider fin spacing to suit the much lower cooling air speeds.

I live in QLD so have never experienced the problems of severe corrosion of the cylinders, but from a corrosion point of view I think paint would be a good idea.

Autostik, a harley is not a good example, as it is a very understressed motor. They make hardly any power for their capacity and as such are not prone to any cooling problems.

I would hardly call myself a fresh graduate, I think 4 yrs of eng industry experience is plenty, especially with it being so specialized in the field of stress analysis and heat transfer / thermodynamics. But there are plenty of much more experience people than me that will still tell you that chrome plating your cylinders would be a very silly thing to do. In fact I think the cheif engineer at Tatra would have told you that.

I never said I had anything against the painting / anodising idea. I said and showed from my results that it made very little difference either way.

[Edited on 27-3-2003 by Baja Wes]

Wes - www.offroadvw.net - 200HP Quad Cam V6 in a VW Baja - with climate control... 🙂
www.taylorcycles.com.au - My DH MTB racing brothers shop.

70AutoStik Insano Dub Head

730 posts · joined Aug 2002 · 27 Mar 2003, 10:33 pm

#34550

I have ridden a bike in a coastal area and the corrosion on cast iron fins doesn't build up to the point of causing a problem as fast as some will have you believe. If you are restoring an old bike from a coastal area (that happens to be healthy enough to be worth it,) simple sand-blasting gets 'em back to original condition pretty quick.

PatB Casual Dubber

32 posts · joined Mar 2003 · 29 Mar 2003, 11:27 pm

#35052

I should add the qualifier to my last post that I'm talking about Japanese engines in the main. I can think of cases among various accquaintances running late 60s and 70s Triumphs and the like (whose engine designs were getting pretty marginal for the power outputs they were being asked to produce) who polished and/or chromed their crankcases and subsequently found that their oil boiled when running hard. However, these were engines that were so overstressed that they needed all the help they could get. I still maintain that anything not already on the limit would barely notice a difference.

70AutoStik Insano Dub Head

730 posts · joined Aug 2002 · 30 Mar 2003, 12:50 am

#35059

Yeah; actually the trumps you are talking about are exactly where anodising and artificially roughing surfaces became popular in the auto industry - personally I think the fins just weren't big enough (but they were/are still wonderful to ride.)

[I should add that the Bonnie had no in-built oil cooling, so after-market finned tranny covers actually made a significant difference - for those who don't know, many bikes share the oil between the engine and tranny.]

[Edited on 29-3-2003 by 70AutoStik]

68AutoBug Beetle Restorer - Experience over 138\% - YIKES --

11,654 posts · joined Aug 2002 · 30 Mar 2003, 6:15 pm

#35169

Thanks Wes, I, glad all that painting I did on My engine and gearbox... doesn't have to come off... LOL....!! I have found that VW Engines corrode very badly, even in the country, laying out in the open.... No Salt etc.. Just Corrosion....

Baja Wes wrote:you paint the case after the engine is assembled, that way you don't get paint in machined surfaces.

The generator and alternator are air cooled and will not suffer from painting.
chrome barrels? are you mental? :o chrome will trap the heat in the barrels, and significantly reduce the turbulence and have negative effects on the boundary layer formation around the fins. This will really reduce heat transfer of the barrels. Never ever chrome your barrels.

Chrome tin ware is ok because it is not directly transferring heat.

:o:thumb:thumb:thumb:thumb:thumb :bounce:bounce:bounce:bounce

- Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY---

Baja Wes V6 Baja Pioneer

3,119 posts · joined Aug 2002 · 30 Mar 2003, 7:35 pm

#35193

I take my baja on the beach, and if you have clean bare magnesium there it gets really attacked. So painting cases and gearboxes is very smart if you plan beach driving. I haven't noticed the cylinders get too bad. They get a light layer of rust but then doesn't corrode any further.

My bike actually has a dry sump design and uses the steel frame to store the oil. My dipstick is in the top of the frame just under the handlebars.

Wes - www.offroadvw.net - 200HP Quad Cam V6 in a VW Baja - with climate control... 🙂
www.taylorcycles.com.au - My DH MTB racing brothers shop.