Different metals in contact with each other

[kenny1999]

I learned in school that when two different metals come in contact with each other accelerated corrosion will occur.

How about alloy and metal with painted surface?

For example, I think that stainless steel is very unreactive / non-reactive. Could it cause
any accelerate corrosion to itself or another metal when it's in contact with different materials?

Also please comment about metal with painted surface . Thanks

 

[HAYAO]

Tell me if this stainless steel is "non-reactive". Unless they are put into perfect vacuum, there are no stainless steel that will not corrode. They will corrode in water, they will corrode in air, one way or another.

That being said, metal with a painted surface has been one of the main ways of preventing corrosion in many different materials. As a matter of fact, metal desks usually have coatings. The "paint" are polymers most of the time, but some lab level research uses organofluorene material, which is extremely hydrophobic and oleophobic. However, some material will enhance corrosion, so it's a case-by-case thing.

Corrosion in alloys is already quite complicated that it already has a research field dedicated to it, with fair bit of long history. As a matter of fact, a simple Iron corroding in water is already quite complex. What happens to when alloys and another metal is in contact is unknown unless you specify exactly what you are working on under what condition. Same here, case-by-case.

 

[Astronuc]

I learned in school that when two different metals come in contact with each other accelerated corrosion will occur.

How about alloy and metal with painted surface?

For example, I think that stainless steel is very unreactive / non-reactive. Could it cause
any accelerate corrosion to itself or another metal when it's in contact with different materials?

Also please comment about metal with painted surface . Thanks

If the paint is coherent and intact (i.e., not cracked), then it will act as a barrier, or insulator, and prevent corrosion. Elements have different electrochemical potential, and one will serve as an anode and the other as a cathode, which is the principal of a battery.

Stainless steel will become passive (low or zero corrosion rate), through the formation of an oxide layer, which is mostly chromia (Cr₂O₃), but the protective nature of the oxide depends on the environment. If too acidic or too basic, or if sufficient halide (fluoride, chloride or bromide) the oxide can breakdown and stainless steel will become active. Seawater, with chlorides and some bromides, can be very corrosive to stainless steel, so surfaces are usually painted, and we use stainless steel alloys with high Cr content, e.g., 20-27 wt% Cr.

Elements and alloys can be ranked according to their electrochemical potential. Note where passive and active 18-8 stainless steels lie with respect to other elements.
https://corrosion-doctors.org/Definitions/galvanic-series.htm#Series_in_Seawater