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corrosion aluminium / steel

  • Thread starter Thread starter pd_frankie
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pd_frankie

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Good morning, everyone.
have any of you found yourself in a situation similar to this?

I have to create an electrical picture to install outdoors, even in coastal areas; for question of costs I have to make it in aluminum sheet peraluman 5754 thickness 2mm with thread inserts m4 in stainless steel 316, all then painted in polyester powders. 316 stainless steel screws will be used on the inserts. we must guarantee 5 years on the product.
galvanic corrosion between insert and aluminum sheet should be prevented from painting; while between insert and screw should be no problem as of the same material. I'm not wrong, am I?

and if the inserts were in normal galvanized steel?

thanks in advance for sharing your experiences.
 
I think you run the risk that paint jumps where you put the insert but depends on how it is done. is he self-tapping? pressure? a solution could be to use plastic inserts or protect the area with duralac.

I've never used it, but I'm afraid it's not a solution. the weak point is aluminum.
 
Thanks, sail.

It's a deformation tube hexagonal rivet. it "aggrappa" with remarkable foreplay to the sheet. is applied before painting.
I trust in the goodness of painting, because aluminum is less noble towards the galvanized steel (as you, rightly) but also towards stainless steel.
 
I repeat, I'm not a field expert, but...

I think if the paint does not isolate aluminum from the steel does not solve the problem. you will have a certain degree of protection from the salty atmosphere (near the sea) but the galvanic will continue to be under the paint.
 
on the aluminum trees of the sailboats often mount rivets in stainless steel and then paint everything. unfailingly after a few years the paint at the rivet inflates due to galvanic corrosion. you try to isolate the two metals conplasty and/or duralac but you never get a perfect insulation. However I think that for 5 years the damage can only be aesthetic or little more.
 
Hi, I'll throw mine.

Couldn't you anodis the aluminum and then finish it all with powder coating? a product with a...
if we want to make the pinions you can use paper seals between sheet and rivet to prevent one from affecting the other.
 
My experience.
peraluman obtained from the full minimum thickness 2.5, surtek (no anodization for compliant rhos), powder coating, certificate ip67, stainless screws.

(so for diving certification, salt mist etc.)

for the galvanic between stainless steel/aluminum I don't know, I trusted the electronics/electronics that I think had made calculations on the ddp without any problems.

the equipment has been out for about 1 year and for now everything ok.

the only thing with anodising are threads, canals etc. that tends to "transud".

I now made another in sheet metal (ip65 to certify) and the main tub I make it in fe01 powder coated, pem in stainless steel inserted after painting.

Bye-bye.
 
x pierarg, paint the anodised is not trivial, if you want it to adhere... the risk is to do worse!
x vale61, anodization is compliant rohs, as long as there is no chromium in any way (but this is not difficult).

In general, to unleash corrosion is not only the electrochemical differential between materials, but also the mass and surface! for example, for panels in aisi 304 no screws are used in 304 (which would be corrupted!), but in 316 (which resists more!).

I share what he said wave, also on the use of elements that break the pile, in plastic type polyolefin. I believe that already ready threaded inserts with plastic crown are on the market, for those who deal with architectural facades.
 
Starting from the assumption that two dissimilar elements will never have to be in direct contact, especially in the sea area where corrosion would have shorter times, you could insert externally treated aluminum inserts (anodic oxidation) technically called aircraft jargon rivenuts, with cadmiata screw! is to consider the functionality of the screws!
 
paint the anodised is not trivial, if you want it to adhere to... the risk is to do worse!
Click to expand...
I thought (or I think) that with powder paint there is no problem. many electric motor manufacturers for marine applications use it
 
starting from the assumption that two dissimilar elements will never have to be in direct contact, especially in the sea area where corrosion would have shorter times, you could insert externally treated aluminum inserts (anodic oxidation), with cadmiata screw! is to consider the functionality of the screws!
Click to expand...
quoto in toto.
or you could use paper seals
 

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