HI All

What is the purpose of painting a locomotive Boiler either Silver or Aluminium just before a test , thank you Pat

The color is irrelevant to a hydro test, what you are seeing is "high temperature aluminum" paint. It is most commonly utilized because it is cheap. It doesn't hold up terribly well, I am yet to see a boiler painted with this stuff have it's jacketing come off and the paint still be intact.
There are much better alternatives available but the run about $150 per gallon versus $40. Is the protection of the exterior not as important as the chemical treatment of the interior?

Cheers, Jason

As an addition, lest a boiler is first blasted to a "near white" finish no product will hold up terribly well. Two reasons for this: 1) any chemical contamination of the grain (sulfur, already formed rust, etc) will ultimately lead to rust forming and a failure of the finish. 2) Even if the metal is clean of contaminants, repeated thermal cycles will cause the finish to "loose it's grip" on the surface. For the finish to provide successful protection it must be able to seep into the open grain for satisfactory adherence.

Cheers, Jason

When doing work in the firebox it is much easier to see what you are doing by painting the firebox silver.

probably a refurbished fresh boiler, get the cheapest workable paint now, have some runs with this steamer make some bucks, then go back at a good time and repaint it correctly. Economics may play a part, protect it now even tho we know it may not hold up in the longevity, we understand it and when the engine is all together it will get the full workover correctly in the future, that would be a good way to go about it. Seems pretty obvious this boiler went out for a workover.

Why would somebody use inferior paint to save $1000 after paying for a boiler overhaul?

Paint doesn't actually do much to protect boilers in service. Cold stored, much more important.

dave

The boiler in the picture is from D&RGW #463, being delivered in Monte Vista, Colorado to Marty Knox who is completing the restoration of the locomotive at that site. The boiler was rebuilt by Bob Yuill at Historic Machinery Services, who is one of the best boiler men in the country.

The interior was painted with special corrosion inhibitors, and the exterior paint was primarily applied to protect the boiler from rust during the delivery from Alabama to Colorado, and during the the time that it will take Marty to complete the rebuild.

So if I understand this correctly, paint on the exterior of the boiler is irrelevant and not even needed once the locomotive is jacketed and operational, but is only applied to prevent rust in the short term between the completion of the boiler and the reassembly of the locomotive.

To clarify a few points:

The purpose of painting the exterior of a boiler, as well as the interior, is to prevent or at least limit corrosion. Corrosion of a boiler exterior will occur especially when the locomotive is stored outdoors with no protection from rain water. Remember, the boiler is insulated, and this insulation will absorb water contributing to corrosion.

In the case of the 463, the interior was blasted and coated with Apexior, the exterior was also blasted and painted, (after repairs and hydro were completed), with a high temp. zinc rich coating. This coating should provide years of protection to the exterior of the boiler, not just in transit time from our shop to Monte Vista.


Robert Yuill
Historic machinery Services
http://www.historicmachneryservices.com

Paint designed to withstand high temperatures - like aluminum paint or BBQ black - is almost always put on boilers exteriors since it doesn't cost much and offers an affordable layer of protection against moisture leaching acids out of soot retained in the insulation beneath the jacket.

Boilers kept in service never have moisture problems, as at atmospheric pressure it boils away at lower temperatures than the boiler itself is under steam.

Gray areas are boilers fired on occasion - the museum that operates one day a month, and keeps rolling stock outside. If that's you, it makes sense to take more pains about maintaining a good exterior coating.

Your mileage may vary.

dave

Here is another product to consider. It can be tinted to suit your desires....

http://www.apexior.com/Products/Products.asp?ProductID=34

Bob.

Thanks for correcting me on the exterior. The intention of my post was to say that neither you nor Marty would have anything done that was anything but the best, and I made an assumption that I should not have made.

Everett

Dave (sutter),

Per the manufacturer, this is the best coating system for steam locomotive boiler exteriors: http://www.apexior.com/Products/Product ... oductID=51

In regards to another post, once a boiler is blasted and painted..... You are stuck with what you put on it unless one plans to blast the boiler again. There is no simple means to go back and put something better on later.

Cheers, Jason