See full version: Can Stainless Steel And Aluminum Be Used Together
When bringing aluminum and steel into contact, you can also use a thin layer of non-absorbent insulate between them. Rubber or plastic can work, depending on the application. You can also use polypropylene tape or prime the parts with a protective coating. Even with such treatments having been done, you should use a corrosion-inhibiting material of some kind – such as pastes, washers, etc. – under the heads of bolts and screws as a further preventive measure. more
One way to be sure is to use the key test. Take a key and drag it along a flat surface. If the surface is aluminum, it will scratch quite deeply without too much pressure, since aluminum is much softer than steel. The steel will not scratch at all or only superficially. more
When the pieces being joined are structural, use the strongest fasteners you can find. For example, when joining aluminum and steel, choose carbon steel bolts.
Along with corrosion, discoloration of stainless steel may occur when combined with aluminum. This is also called ‘tea staining’. Discoloration can be prevented by the use of insulation and regular maintenance. Passivation can also be used to create the passive film on the fastener for better corrosion resistance.
When using stainless steel fasteners with aluminum surfaces, you can prevent corrosion by placing something between the two metals. Plastic or rubber washers or gaskets are good suggestions.
Not sure what materials you’re dealing with? It’s usually possible to till the difference between aluminum and stainless by sight, as the former has a duller appearance. Aluminum is also much lighter and softer than steel. However, it isn’t always so obvious; it depends on the alloys in question. Different manufacturing processes can create different appearances and finishes.
Buy your bolts at a good marine store, such as West Marine. If they don't
have the grade marked, use a magnet to insure you're getting a low carbon
variety. If the magnet does not stick at all, it's low carbon. By the
way, this is a good test when you're buying hose clamps. Many stainless
hose clamps are made of 308, and sometimes the screw is, even when the
clamp is not. In a wet bilge you will get some corrosion on the 308, and
could get a failure.
The situation becomes more complicated when we consider the effects of
carbon. Carbon likes to stabilize a phase of steel called martinsite (this
is close to the bcc phase, actually body centered tetragonal). The effect
is especially noticeable in type 304 stainless, where martinsite can be
introduced in the metal by simply cold working it (deforming it at room
temperature). [links]
The effect of the potential difference is mostly on the speed of the
corrosion rate. A larger difference will give a faster rate of corrosion of
the less noble metal and a slower rate of corrosion for the more noble
metal, as compared to the behavior of these metals when they are not in
contact. Even different alloys of the same metal, such as 1100 aluminum and
6061 aluminum or 304 SS and 316 SS, will develop a small potential
difference because their compositions are different. These differences are
comparatively small but none-the-less could give rise to noticeable
effects.The best solution is to work with materials that have inherently
good corrosion resistence to begin with. here
Consequently, does Flex Seal really work on boats? here
Can you really patch a huge hole in a boat with flex seal? Flex Seal, the "miracle cure" liquid-rubber material makes some pretty bold claims in their numerous TV commercials. In fairness, the boat did float. It didn't last very long, but it did float long enough for him to catch a fish! here
How do you apply Gluvit to aluminum boat? [links]
Beside above, what can I use to seal aluminum? Use Gluvit on aluminum fishing boats to repair leaky aluminum seams and rivets. The cure rate has a long working time that allows penetration into cracks to seal and strengthen. Gluvit fills minor chips and pinholes, and is easily painted with most bottom or topside coatings and paints.
The CUP sealed blind rivets are made of 316 stainless steel for the body and the mandrel from 318L Duplex and tested to demonstrate 100% waterproof. The video clearly shows the water seeping through the traditional blind or pop rivet, yet our closed cup rivet remains 100% waterproof with up to 1 metre of water.
A lot of guys use these on a boat and the same thing, as far as a car goes, for these items. And if you're down by the shore, by the beach, these are items that you're gonna want to use on your car that will not rust. If you use 18-8 stainless steel on your car and you live down by the beach, this will show rust over time. You will not be a happy camper. [links]
I have here everything not to use in a saltwater application. Okay, I have here a grade 2, a grade 5 and a grade 8 zinc coated fastener. I have a thermal black oxy coated fastener, also, black oxy stainless should not be used in a saltwater application. 18-8 or 304 stainless steel should not be used in a saltwater environment. This will surface rust and that will happen in the first week. You'll start to see surface rust or within 30 days. Hot dip galvanized (zinc) - you can use this in the (saltwater) environment. However, over time, you're going to see this rust depending on temperature, the weather, many different scenarios make that product rust. here
Bob: Hey, Welcome back to Albany County Fasteners - Fasteners 101. Today we're going to talk about everything saltwater. So, let's get started. Saltwater environments are everything within 20 miles of a saltwater ocean. Wherever you have salt water, within 20 miles you should have a fastener that is made out of 316 stainless, aluminum or silicon bronze. more
I have here all the items that you do want to use. This is aluminum, so that can be used in a saltwater environment and will not rust. This is a 316 stainless hex cap screw. This also will not rust and in a saltwater environment. Silicon Bronze, silicon bronze, will not rust. however, it will patina over time. So that is an item that can be used and that's one of the best items that can be used but you may not like the aesthetics of how it's gonna look over time. here
Whether its a boat, dock, marina or just by the ocean, most fasteners don't stand up to the corrosive properties of saltwater environments. To combat this, Albany County Fasteners has created this page for you, the customer, to provide everything we offer that Will last in a marine environment in a simple easy to browse category. Find everything you need in 316 marine grade stainless steel and silicon bronze; both with properties to withstand the test of these harsh environments. Don't forget to purchase a bottle of Marine Grade MRO Anti-Seize Solution with your fasteners to make installation easy and increase the life of your fasteners even longer!
When I worked at a shop that built training models for NASA's training tanks we used aluminum material, stainless bolts and brass bolts.
Used some staimess nuts but they didn't disassemble easily.
Passivating and electropolishing are both techniques to clean the surface of stainless- like you said, they strip off any contamination from grinding wheels that have been used on steel, spatter from steel wire feeders, even scrapes from forklift forks.here
Passivating is a more gentle process, mostly a dip as I understand it, which leaves a dull gray mill finish looking end product.
Electropolishing uses high amperage power supplies and a heated acid bath to agressively strip off the top layer of the stainless, leaving it shiny.
One of these is a good idea for shop fabricated stainless items that will be out in the weather- otherwise rust spots can show up, months later. These rust spots are just surface contamination, and can be taken off with a clean stainless wire brush in most cases.