Aluminum Machine Screws vs Stainless

[cbt0011]

Can anyone point me to a thread discussing aluminum vs stainless machine screws? I'm needing to reattached the frame on my plexi window/rockguard and it used what look to be steel or galvanized... My worry with aluminum is shear strength, my worry with stainless is Galvanic Corrosion... Any help is appreciated

[Crackerman]

Stainless steel and aluminum are very similar in range on the galvanic scale. Use stainless hardware. It will be fine.

[GMFL]

Stainless steel well not cause a problem.

[pjshier]

as said, it will not be a significant problem because both metals generally are close on the galvanic scale, though some alloys of aluminum will be farther up the scale. If you are uber retentive and want to feel like you have gone the extra mile, you can
1. put the fasteners in a baggie and spray some Boeshield T-9 in the bag with the fasteners. Then pull each fastener out of the baggie just before installation, wiping off any excess after the whole job is done.
2. pass the fastener through a slim nylon washer instead of or in addition to #1 above. Both would be belt and suspenders approach.

We did these things to airframes in marine environments, very effective in preventing even the occasional reluctant galvanic corrosion that inevitably occurs in such environments.

[JeffE]

You can prevent/control dissimilar metal corrosion by coating the fasteners with tef-gel.

Jeff

[Ricky Bobby]

Buy the best stainless steel- not from Big box stores.

[Ricky Bobby]

Look at this chart on the web. Dissimilar Metals in Contact

[Hermes]

I think the thread you are looking for is this one:

https://www.airforums.com/forums/f4/...ml#post2334840

Here is the opinion of the British Stainless Steel Association. There would seem to be low risk of corrosion of using stainless steel:

https://www.bssa.org.uk/topics.php?article=89

Corrosion risks with aluminium and stainless steel in contact
Aluminium and stainless steel together also appears to be a bi-metallic corrosion risk, from the 'nobility' table. With this combination the affect of relative surface area on corrosion is important.

A large area of 'cathode' relative to 'anode' will accelerate the anodic corrosion. Although aluminium is anodic to stainless steel, large relative surface areas of aluminium to stainless steel can be acceptable, dependant on local conditions. Stainless steel fasteners in aluminium plates or sheets are normally considered safe, whereas aluminium rivets or bolts holding stainless steel parts together is an unwise combination, as there is a practical risk of corrosion.