Hot Roll Mild Steel A36? Corrosion with Copper?

[jamesavery22]

Im going to build a few cheapo blocks for VRMs and HDs. Rectangle and square copper tube is what Id really like to get. Online metals doesnt have any though =\ They do have Hot Roll Mild Steel Rectangle Tube A36? Its VERY cheap. Like 1$ a foot for a 1" x 2" rectangle tube.
Googled it quickly and just found out it was popular in bridges after 1930, didnt really help me much. Sounds like if its not coated corrosion will be a problem.

With this cheap common steel and copper will I have problems if I use anti-corrosion additives(polypropelene glycol antifreeze, distilled, iodine)?

Buying that stuff would chop a good 50$ off of my total from online metals.

[Moto7451]

With anticorrosion agents in place I would imagine that you'll have no problem.

[jamesavery22]

The aluminum square/rectangle tube isnt that much more expensive. But Im guessing steel + copper + water would cause less corrosion than aluminum + copper + water?

Just need to get a .125" x 12" x 6" plate of c110 copper now =\ Anyone wanna split a 12" x 12" plate with me? :D

[Moto7451]

Actually if its going to corrode I would guess it would corrode in the same proportion as there are the same number of molecules in one mole of Steel as there are in one mole of Aluminum. In english, for the a volume of one material there will be the same number of molecules as in the same volume of a different material. Anyways, I suppose it all comes down to: Does Steel oxidize copper? From the looks of it it does in Vinegar at least.

1. CuO + HAc --> Cu(2+) + Ac(-) + OH(-)

2. Fe --> Fe(2+) + 2e(-)

3. Cu(2+) + 2e(-) --> Cu

In this case 2 & 3 will happen on the piece of Steel (remember that Steel is made of Iron)

The overall equation for that is:

Fe + Cu(2+) -> Fe(2+) + Cu

The Copper will plate the Steel.T his example was found here (http://www.madsci.org/posts/archives/feb98/888588896.Ch.r.html) & I added to it using stuff I remember from Chem class.

In theory I would imagine in water you're getting the same system if you can get Copper ions into the water somehow. You could follow the link I showed you to plate your Steel with Copper which could inhibit corrosion.

[jamesavery22]

Thanks Moto,
that kinda sucks. Looks like it would be beneficial to just either find copper or brass square tube or find some cheap 48oz copper sheets and make the tops out of em =\

[rogerdugans]

I am not a chemist and I take a lot of stuff for granted when it comes to that topic- you guys teach me and so do my jobs.

I am currently working as a welder/pipefitter in the heating industry and most of what I do is install heating and domestic (drinkable) hot water systems.

ANY water that is drinkable can be in contact with a very limited number of metals: brass and copper are the main ones. Some stainless steels are allowed in SMALL amounts.

Iron pipe is absolutely not allowed. ;)

It will contaminate and corrode the system.

Now we can and do use mixes of copper and iron pipe in heating systems, but the copper is not expected to last as long as it would in a domestic water system...

My long winded point?
While it is possible, and might be ok in the short term, mixing copper and any steel containing iron is going to cause problems eventually, and as "delicate" as a water cooling system is (at least for good performance) it would probably be a bad idea.

Just thought I'd toss in my small bit of knowledge in this area. ;)

[jamesavery22]

Thanks,
definitely just gonna go all copper and avoid the cheap route.

[robjen]

Here is an idea. When I was down at the local salvage yard, they had a huge box of copper pipe, some of it 3 in in diameter.

Just get some of it and slit it down the middle and flatten it out. Then reshape it into a square tube and solder it together.

Just an Idea

[ls7corvete]

STF, I beleive you will find some corrosion due to steel/iron.