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Post by scootman on Aug 9, 2007 0:29:02 GMT 10
Hey all.
Ok I know that you cant put aluminuim with galvanised iron cost it causes it to rust. But can you put Stainless stell with aluminuim?
The reason I ask is because some, not all, but some of the screws that I used to put the J mould on, have rusted. They were stainless steel. The J mould is aluminium?
Thanks Scoot
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Post by Deleted on Aug 9, 2007 7:34:27 GMT 10
Hi Scooty methinks you have been sold a dud. Those shiney screws you used must have been "chinese stainless steel".... in other words poorly zinc coated mild steel.  Staino and aluminium usually get along Ok together. used em for years on a few Half cabin outside fishing boats i have owned in the past.  Then there is the issue of what grade of stainless the screws are made of. Not all that full bottle on the numbering system but i know there is a difference between cooking grade staino and Marine grade....  My 2 bobs worth... thanks for listening  . Reddo |
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Post by Franklin1 on Aug 9, 2007 9:21:51 GMT 10
Scoot, I have metallurgical qualifications, and agree with the guys above. Yes, there are various grades of good quality stainless steel, as there are of aluminium. But irrespective of the grades, all stainless steel is less corrosive than aluminium. When you combine s/s with ali in a moist environment, it will be the ali that corrodes preferentially (ie. before) the s/s. Having said that, one overriding condition is whether the s/s is "good quality". Some imported s/s does not have the same nickel/chrome composition as good quality stuff, and can prematurely corrode. The same experience can be had with buying supposed Grade 3 hot-dipped galvanised screws from the hardware store. Most are now imported, and after six months of exposure on a fencing project recently, I found that some of the screws were showing significant rusting. I was p**d off...you think you're using quality stuff and it turns out to be crap!
cheers,
Al.
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Post by scootman on Aug 9, 2007 11:03:16 GMT 10
OH well. I guess I will have to take them all out and replace them with better quality. I dont really want to do this, I went to great lengths to ensure that there would be no chance at all of it leaking from screw holes using a solastic to put the moulding on then screwing the screws into that then wiping it all of with spirits. DAM!
Scoot
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Post by Roehm3108 on Aug 9, 2007 17:40:38 GMT 10
What's even worse is paying quality prices for cheap imitation stuff and finding out AFTER you've done the work! Bad luck Scoot.
Ray
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Post by humpty2 on Aug 9, 2007 20:00:12 GMT 10
I have a magnetic welding assist for 90 deg & 45 deg joints.....verrrrrry strong magnet. I pass this over any scews or bolts that I use purporting to be stainless or brass........yes they brass coat mild steel the cheeky buggers  You would be surprised at the number of screws etc that look like stainless that it picks up. I also do a little work on some boats and S/S or brass is a must! |
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Post by scootman on Aug 9, 2007 22:42:16 GMT 10
so a magnet wont pick up stainless or brass? or it will?
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Post by humpty2 on Aug 10, 2007 20:36:54 GMT 10
Magnet won't pick up good quality stainless ..and definately not brass.
Not hard to find a good magnet..........the back end of a speaker is powerful enough!
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Post by Franklin1 on Aug 10, 2007 22:34:42 GMT 10
Can I clarify the magnetic properties of stainless steel? I'll copy and paste some web information to speak for me... "Is stainless steel magnetic? Does it depend on the amount of chromium, or nickel alloy?
Asked by: James McGuigan
Answer
Stainless steels are a very broad group of metals. The name was adopted as a generic term for steel alloys with a minimum of 10.5% chromium. The chromium gives the steel its 'stainless' properties - essentially corrosion resistance. On the surface of the metal, a very thin chromium-rich oxide layer is formed which is inert - i.e. it prevents the steel from rusting. The advantage of stainless steels over plated steels is that, if scratched or damaged, the steel will 'self-repair' as a new oxide layer is formed. In plated steels, scratches in the plate will often lead to corrosion of the steel underneath.
In general, the higher the proportion of chromium, the stronger the corrosion resistance of the steel. In addition to chromium, other metals are added to give the steel particular properties such as strength and malleability. Specifically nickel is used to strengthen the oxide layer.
As for whether they are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.
So the answer is yes, the magnetic properties of stainless steel are very dependent on the elements added into the alloy, and specifically the addition of nickel can change the structure from magnetic to non-magnetic.
The following company website has a useful high-level definition of the broad stainless steel categories. www.parkrow.org/stainless_steel.htm
Answered by: Jules Seeley, M.S., Physics graduate; Strategy Consultant, London."Hope this helps, cheers, Al. |
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Post by Franklin1 on Aug 10, 2007 22:40:11 GMT 10
Oops, the link at the bottom of the answer is now redundant. Sorry.
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Post by scootman on Aug 11, 2007 1:27:34 GMT 10
Wow thats REALLY interesting. ! Thanks for that. I have had to read the post three or four times to understand it but I do the same thing opening a vita brit box. no, Im not being sarcastic , it really is interesting so next time I go to buy SS screws I will take my magnet with me.
Scoot
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Post by humpty2 on Aug 11, 2007 20:26:00 GMT 10
Works for me ;D
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Post by organichead on Sept 28, 2007 23:58:17 GMT 10
This has been very helpful folks, thanks. I will ask all the realivant questions in the future. If there's one thing I hate it's trying to do quality work only to be let down by poor materials.
Sounds as though trades discription should be informed for better labeling. Afterall scoot youv'e paid for quality and recieved crap. I'd be staight back to the suppliers to insert a few in their cash register. Not forgeting the labour!.
.....................org for better stuff.........................
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