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Steel vs Wood
http://diyaudioprojects.com/Forum/viewtopic.php?f=14&t=5874
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Author:  Steph [ 30 Mar 2017, 19:45 ]
Post subject:  Steel vs Wood

Hello all,

I'm starting the assembly of a new project. With this project I've decided to build a wooden chassis made of walnut with a steel top. I had intended to prime and paint the top and leave the underside untreated. The wood chassis frame has a rabbet edge to allow for the steel top to sit down and become flush with the wood. My thinking for leaving the underside untreated was to minimize the possibility that the paint might stick to the wood and become difficult to remove if necessary and if I had to force it off, my concern is that it might damage the wood. I plan to treat/finish the wood with a tung oil.

After having been working on this for a week or so, the top going on and off several times, I'm noticing some sort of blackening of the wood where the steel makes contact. It even looks as though something may be reacting with or leaching into the wood. I haven't yet applied any paint to the metal and the wood is still unfinished. I plan to save these two steps for near the end after all my test fitting is complete.

Has anyone run into this before? Are there some best practices I should know about?



Thank you,
-Steph

Author:  Geek [ 31 Mar 2017, 00:34 ]
Post subject:  Re: Steel vs Wood

Uh, I haven't :confused:

Do you know the alloy of steel?

Author:  Steph [ 31 Mar 2017, 06:21 ]
Post subject:  Re: Steel vs Wood

I surely do not. It's a 14 gauge panel that I picked up at the hardware store. I've cleaned it and it's been exposed to the open air (albeit rather dry climate here) for a few weeks now and there doesn't appear to be any discoloration of the metal and no surface rust. At this point I'm considering a strip of painters tape around the bottom side near the edge where it may contact the wood.

thanks for the consideration.

Author:  Peter W. [ 31 Mar 2017, 06:28 ]
Post subject:  Re: Steel vs Wood

What is the wood? Oak will get darker when exposed to any sort of finishing chemicals, moisture or for any of several other reasons. Whoops - I see you wrote Walnut! Walnut will suck up any microscopic materials on the steel, so the rolling lubricant is now the most likely suspect.

Unless you need the steel panel to be unfinished for grounding and connection reasons, a half-dozen light coats of Krylon Workable Fixatif (accept no substitutes), will do a good job of sealing the steel from the wood, without changing the appearance. If you do need to connect to the steel and have good contact, install these little rings at each fastening point, ( http://www.target.com/p/binder-hole-rei ... lsrc=aw.ds ) prior to spraying the Krylon. It works.

Keep in mind that steel sold in the manner you describe is pretty much straight off the rolling mill, and is covered with a very fine layer of rolling lubricant. This stuff is an interesting mixture of rendered fat, wetting agents and other materials and is probably the actual cause of your darkened wood. Removing this stuff takes either a very strong solvent or extremely hot water and a very strong cleaning agent such as TSP - altogether environmentally nasty. But in small amounts, not so bad.

Oxalic Acid will remove the darkening from Walnut - use it with great care, however. This may be had at about any hardware store or paint store.

Good luck with it!

Author:  Steph [ 31 Mar 2017, 11:51 ]
Post subject:  Re: Steel vs Wood

That's some very helpful information...thank you very much!

Author:  Peter W. [ 31 Mar 2017, 11:58 ]
Post subject:  Re: Steel vs Wood

You are most welcome! People who build their own chassis are to be admired!

Author:  Steph [ 31 Mar 2017, 13:32 ]
Post subject:  Re: Steel vs Wood

Well, this is my first attempt at this. I raised the grain a few days ago getting ready for sanding and finish so it's still very dull looking. I'm hoping that after sanding and oil that the purple heart miter splines will pop out a bit. I've got a lot of work to do yet.

Here are a few photos...not quite sure how to do this.

http://imgur.com/a/PA2hc

http://imgur.com/a/LTgRb

http://imgur.com/a/3yWGC

http://imgur.com/a/aiZnx

Author:  Suncalc [ 01 Apr 2017, 15:50 ]
Post subject:  Re: Steel vs Wood

Looks awesome! Good work!

Author:  Steph [ 01 Apr 2017, 16:42 ]
Post subject:  Re: Steel vs Wood

I thank you sir for the kind words.

Author:  mwhouston [ 17 Apr 2017, 06:50 ]
Post subject:  Re: Steel vs Wood

I always prime and spray my top plates. I use an etch primer and epoxy enamel paint. The metal surface is prepared with a 320 grit. I never spray the underneath of the top plate. But my bases are always sealed before the Al top plate goes on. Sometimes oiled or spray polyurethane. Therefore there is always a sealed layer between metal and wood.

Your base looks good.

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