4130 question for you guys....

[kevbooth]

I posted on the main forum too, but I thought you motorheads might be able to help also. And seeing as how this project has something to do with motorsports, I figured it would be worth a shot.

I'm building an engine stand for a buddies airboat, using 4130 tubing, 1" and 1.5" x .120 wall, using ER80S-D2 filler. Question is this, after completion he plans to have it powder coated. I'm afraid that the heat from baking the powder coat (450 F) is going to have a bad affect on the tubing and/or the welds. Do I have a valid concern? If so do any of you know of anyother rust preventive coatings (other than paint) that we might be able to use instead?

Thanks in advance.

Later,
Kev

[Hankl]

I'm afraid that the heat from baking the powder coat (450 F) is going to have a bad affect on the tubing and/or the welds. Do I have a valid concern? If so do any of you know of another rust preventive coatings (other than paint) that we might be able to use instead?

Thanks in advance.

Later,
Kev

No Problem. that's not enough heat to affect either the tubing or welds.

Hank

[Aerometalworker]

Kev,
Glad you asked, good question. Over the years there have been found a couple problems with powdercoating 4130.

1-Depending on the process, there is a chance for hydrogen embrittlement of the 4130 durring the baking process, slight, but there is a chance.

2-Powder coat doesn't have any sacraficial elements in it, and along with its other properties makes it poor for corrosion prevention should the coating be chipped or otherwise broken.

3-The powdercoat tends to hide cracks that may develop in the structure, and can elude routine inspections.


One of the best processes for areas of high corrosion ( near salt water, humid areas ), is using a Zinc Chromate primer, or a Chromate Epoxy primer, topcoated with a single component enamel ( synthetic or acrylic ). Using a 2 part topcoat over a single part primer can lead to filiform corrosion, and is a no-no. Using a single part top coat means the coating is not cross-linked, and allows oxygen to get to the sacrifical elements in the primer, which prevents corrosion should the paint coating be chipped.

www.aircraftspruce.com should have all the materials you need.

-Aaron

[Champagneracing]

Go right one ahead and Powder coat away. Just about ever sprint car in the country is powdercoated and ever Super comp and super gas car I ever built was powdercoated as well. A few have hit walls hard and no powder coating job has made any of the cars weak in anyway.

[Synchroman]

Kev,
Glad you asked, good question. Over the years there have been found a couple problems with powdercoating 4130.

1-Depending on the process, there is a chance for hydrogen embrittlement of the 4130 durring the baking process, slight, but there is a chance.

<snip>

-Aaron

Hi,

I'm just curious about the issue of hydrogen embrittlement. In my former life, about three careers ago, I worked as a Rocket Engine Technician at Rocketdyne when it was a division of North American Aviation. I later worked at Lockheed, Litton and Rockwell B-1. I was a technical writer for several years also. The reason I mention this is that during these various positions, I became aware that heat treating is/was used after welding and plating of components to drive off excess hydrogen to lessen the chance of hydrogen embrittlement. The processes to which I refer often specified as much as 12-18 hours in a large oven at something like 300 degrees. F.

I also have a home-built powdercoat oven that is nearing completion. It's 2' X 3' X 6' inside and will be used for Motorcycle frames, wheels and so forth, among other things. I'm not a chemist or a metalurgist, just a little curious. Do you think that heat could cause embrittlement? I always understood that it would drive off hydrogen to relieve the parts. I sure wouldn't want to cause anything like hydrogen embrittlement.

Synchroman, Curious in Sacramento County, California.

[Aerometalworker]

Hi,

I'm just curious about the issue of hydrogen embrittlement. In my former life, about three careers ago, I worked as a Rocket Engine Technician at Rocketdyne when it was a division of North American Aviation. I later worked at Lockheed, Litton and Rockwell B-1. I was a technical writer for several years also. The reason I mention this is that during these various positions, I became aware that heat treating is/was used after welding and plating of components to drive off excess hydrogen to lessen the chance of hydrogen embrittlement. The processes to which I refer often specified as much as 12-18 hours in a large oven at something like 300 degrees. F.

I also have a home-built powdercoat oven that is nearing completion. It's 2' X 3' X 6' inside and will be used for Motorcycle frames, wheels and so forth, among other things. I'm not a chemist or a metalurgist, just a little curious. Do you think that heat could cause embrittlement? I always understood that it would drive off hydrogen to relieve the parts. I sure wouldn't want to cause anything like hydrogen embrittlement.

Synchroman, Curious in Sacramento County, California.

Synchroman,
I wouldnt be too concerned. It was only a couple specific companies materials that had problems, and that was years ago. Basicly the powders they used would release hydrogen when fused, but as I recall it was one of the older 500 degree plus systems. So like I said, there is a remote chance based on the process, however, a 12 hour bake at 350 F will usually drive it back out. From a service aspect I never found the powdercoats too desireable, but its more of personal taste. Hiding of cracks and corrosion getting under the material always bothered me.

I forgot to add in my post about corrosion control, be sure the tubes are sealed by welding, and if they arent you may want to slosh them with boiled linseed oil or LPS3.

-Aaron

[Sberry]

Just out of curiosity how closely engineered is this frame? Lots of things are moot if its a home brew deal or overbuilt, etc.

[Broccoli1]

Why 4130 for a STAND ?

[Synchroman]

Why 4130 for a STAND ?

I wondered about that too. Apparently the "stand" will be the motor mount that holds the engine in place on the air boat when it's running and under way.....I guess that something less could be used unless there's a lot of stress and vibration.

[Aerometalworker]

I wondered about that too. Apparently the "stand" will be the motor mount that holds the engine in place on the air boat when it's running and under way.....I guess that something less could be used unless there's a lot of stress and vibration.

my guess was engine mount as well. And by the sizing given, I was assuming a converted automotive engine. Something quite heavy.
-Aaron