If there is salt content there is a potential for corrosion

for years we have used galvanized straps, screws and nails in contact with salt borne PT and fire retardant lumber .........

OOPS! now it it no longer code compliant because after 30 some years of actual use it was found there was a corrosive reaction.

If you want a nice interior finish, just use drywall

Chris:

Glad you have found this thread.

In your opinion, what potential benefits are there to using MGO in SIPS over steel? I understand the potential limitations of OSB--I'm not sure how MGO stacks up against steel.

Is it mostly just the opportunity for a finished interior surface w/o drywall?

Is there a company currently competing in your markets with MGO SIPS other than Magwall?

24692x;

I see no advantage to eliminate drywall, I have not come across Magwall in our area.

I recently attended a "high wind" design seminar sponsored by Simpson Strong Tie. The word from Simpson is that they make three "categories" of fasteners and two of them are corrosion resistant. The most common fasteners are not corrosion resistant, the second category is zinc plated and is recommended for coastal areas and other corrosive environments with increased corrosion such as coastal environments and some commercial or industrial environments. The third category is the most corrosion resistant (I do not remember the corrosion inhibitor) but it is recommended for beach front and other more corrosive environments. The Simpson engineered products catalog provided a wealth of information on each category and each individual fastener. Most fasteners are available in zinc platted and their other corrosion resistant system.

I am personally glad to see issues such as Mg Cl come up. We can not fix what we do not know about, and unfortunately just because we know about "it" does not mean we know how to fix "it".

Matt B. Phelps, P.E., R.S.

Mr. Mills.. if you know of an ASTM test that we can do to show our MgO Board is not corrosive to the steel issue our board is up to the challenge..I will do it and make it public..if I can convince you ..the rest of the world will be a peice of cake..FYI..except for our fasteners we dont use steel in our SIPS

MD, how do you qualify fasteners for your boards? Do you specify that they should be stainless? Or, what fasteners do you recommend?

Back in the 30's and 40's (I read about this several years ago, so I may be mistaken on the time frame), in large cities on the east coast, builders were using MOC as an admix for cement. The MOC caused the concrete to harden much faster, and with greatly improved early strength. That allowed them to build multi-story buildings much more quickly.

It worked out very well for them, until about 20 to 30 years later. That is when the metal fire-escapes hanging on the outside of those buildings started collapsing down onto the sidewalks below them. That is when they discovered that the MgCl2 from the MOC had severely corroded away the metal supports for the fire escapes, such that they couldn't even bear it's weight. Just imagine if there had been a fire in one of those buildings.

Of course, that is also when the usage of MOC additives was banned as well. That is also why everyone is extremely wary of anything MOC based today. Metal Lathe can't be used in MOC cements today, but metal lathe can't be used in portland cements or stuccoes with calcium chloride either.

But, I would suspect that the biggest issue with MGO (MOC) Board would be in finding fastener manufacturers who will guarantee their products for use in the MGO Board. And, the fact that you guys call your boards MGO as opposed to MOC, is a marketing issue, because you don't want your product to be identified with MgCl2... and it is a bit misleading.

If you want a nice interior finish, just use drywall

Drywall isn't fire proof. It is fire resistant, but MGO board is as close as one can get to fire proof. MOC is a refractory cement, and is used in steam generators and kilns. It can also be finished very nicely for interior applications with a color coat of perfectly non-toxic and fire proof MOC mortar.

Dick;

I agree that drywall is not fire proof, however anything man made has a failure point,  the wall veneer being either fire resistant or near fire proof is of little value when there are plenty of other combustibles in a dwelling.
While there are plenty of drywall hangers and finishers available, I don't know of  many MGO/ mortar plasterers.

When you set a MagWall MgO SIP it is ready to finish.. stucco the outside knock down the inside and walk

While there are plenty of drywall hangers and finishers available, I don't know of many MGO/ mortar plasterers.

Do you know anyone who applies stucco color coats? Same skill set with drop cloths.

So, MagDaddy, do you require stainless steel fasteners for your MGO Boards?

Posted By MagDaddy on 14 Feb 2010 03:42 PM
When you set a MagWall MgO SIP it is ready to finish.. stucco the outside knock down the inside and walk

No joint prep?

Fiberglass mesh tape, the coat is about 1/8" thick.

D'Oh!  I thought you were talking to me, Chris. 

Dick;

thats OK, the point is its a little more than knocking down and walking away, then what gets used on ceilings and interior partitions? What is roof assembly made with?

Last year I visited a few MGO factories in China. They had some tanks and the MGO was in those tanks in water for 10 days , this way it was getting really white in color. Also the MGO has been subjected to a controlled immersion test where samples of 10mm and 14mm thick  were placed in closed container of water and exposed to freeze and thaw cycles for a period of 36 months. At the completion of the test, there was no appreciable change in the physical properties of MGO.

http://www.mag-board.com/properties.html

So I think that this corrosion problem that is being questioned about this product is nothing compare with the advantages that are regarding this product. The corrosion problem can be very easy avoided by using coated or stainless steel screws and hangers. I am amazed that we are so hard to change to a new and better product. I do have a sample of MGO SIP in my hand from MagWall and I can tell that they are doing a great job, the best construction product ever. It is all in one, ready to be finished.

Liviu, that white color is more than likely a process called efflorescence. Efflorescence is where the salt (in this case MgCl2) is leaching out of the board. And, that salt (more specifically the leaching out of that salt) is very corollary to what the problem is. That there is some quantity of free salt in the compound means that it can come into contact with metals that could corrode.

The general work-around for that free salt is to add more MGO to the mixture than is necessary, the thought being that there would be free MGO, and much less free MgCl2. And, bear in mind that the MGO is the expensive component, and that an imbalance in the compound results in a weaker bond. Adding more MGO doesn't always work, though, and requires very good quality control procedures.

And, like I mentioned earlier, the construction industry was burned once by MOC, so no one is particularly interested in potentially being burned by it again.

Dick, I am sure you are right about the process. I still think that is way better than OSB SIP's. Even if  you use stainless screws and it is a little more expansive, the final product is a much better  building.

Liviu, I don't disagree with you, but I need proof that MGO board is a better solution, and that it doesn't introduce other significant problems. And, more than just me, the entire industry needs that proof before any mass migration will ever occur.

If those who are manufacturing and selling MGO boards know the answers to those questions, then they should be talking. That they are not, to me says that they either don't know (which is bad enough). Or they do know, but the answers don't benefit their sales (which would be criminal). Either way, it doesn't engender much confidence in the product.

Dick, I hope this is enough to make a decision. Sorry for the chart posting is out of alignment.




Value                                  MAGBOARD        Cement            Plywood     Gypsum                          Gypsum                   O.S.B. 
                                                                                                               Walboard                         Sheating

Flame Spread                           0                        0                  High          Low/15                             Low/10                  High 
 
Smoke Developed                   None                 None              High          Low                                   Low                      High

Water Resistant                       Yes                    No                  No             No                                      No                        No

Mold/Mildew Resistant             Yes                    Yes                 No             No                                      No                        No

Termite Resistant                      Yes                    Yes                 No            Yes                                     Yes                       No
Thermal Insulation
R-Value per inch                       1.2                     0.8                1.2             0.9                                     1.1                       1.0

Impact Strength                       High                   Medium          High          Low                                    Low                     Medium

Weight lbs/sq.ft.                     2.2                     3.1                1.6             1.9                                      2.4                        2.0

Combustibility                          Non                    Non               Burns      Facing                               Facing                       Burns

Structural                                 Yes                     No                 Yes            No                                      No                        Yes

Environmental                         Good                   Good             Good          OK                                       OK                        Poor 

Freeze/Thaw                           Good                   Good             Good          Poor                                   Poor                      Good

Finish Interior                       Tape and                 Provide         Provide     Tape and                           Tape and                Provide  
                                                 paint                 cladding         cladding       paint                                  paint                  cladding



Exterior                               Apply stucco                     N/A          Apply paper    N/A                           Apply stucco               Apply                                         or cladding                                             and stucco                                       or cladding            paper and stucco 
                                                                                                    or cladding                                                                    or cladding