What is the difference between double and single shielded bearings, next question is why are reels like the diawa BG or penn fierce/slammer marketed toward saltwater when they don't seem to have any sealed system to keep salt out of the gears and internals. The only difference I read was that the bearings on these reels are either shielded or sealed, and have ant aluminum body

Beginning with aluminum, the bare metal is not salt resistant, but the anodized metal is both hard and salt resistant.  Anodized magnesium is also salt resistant, but not as hard, and bare magnesium corrodes much more rapidly in salt than bare aluminum.   While brass drives have good life in salt, the best salt reels use stainless steel drives. 

 

What you'll find with all good spinning reels (even Tica) are sealed A/R bearings (p/n 41).  Shimano calls their strategic use of seals X-Shield. 

 

Daiwa uses mag-seal bearings in the drives of their higher-grade reels.  The balance of materials are salt resistant. 

 

Consider all my reels to be salt reels.  None get shielded spool bearings, but those aimed at salt get salt-resistant unshielded spool bearings.  The way I look at shielded bearings, salt water in, steam out, salt concentrates behind the bearing shield.  With my salt-resistant unshielded bearings, I flush them every time I oil them. These are KTF spool bearings. 

The one thing you can't do anything about is cathodic coatings on magnets, and these need to be inspected and replaced when they show the beginning filiform corrosion.  This was after 4 years exclusive salt use.  Note that the corrosion products of metals in salt are more corrosive than the salt itself.  E.g., Ferric chloride and cupric chloride are strong acid oxidizers - if you see a rusty bearing, get it out of there, no cleaning will help. 

 

I tried full zirconia spool bearings in my surf reel, but couldn't stand the noise, and went back to MTCW spool bearings (the ZrO are in my back-up mono spools now). 

Fully sealed reels, Van Staal, IRT, are really for the surf, and then, primarily for the NE surf.  Sand slurry from the surf is a greater concern than salt.  Labyrinth seals, such as Shimano X-Protect are everything you need if you're not going to dunk your reel and leave it. 

1 hour ago, bulldog1935 said:

Beginning with aluminum, the bare metal is not salt resistant, but the anodized metal is both hard and salt resistant.  Anodized magnesium is also salt resistant, but not as hard, and bare magnesium corrodes much more rapidly in salt than bare aluminum.   While brass drives have good life in salt, the best salt reels use stainless steel drives. 

 

What you'll find with all good spinning reels (even Tica) are sealed A/R bearings (p/n 41).  Shimano calls their strategic use of seals X-Shield. 

 

Daiwa uses mag-seal bearings in the drives of their higher-grade reels.  The balance of materials are salt resistant. 

 

Consider all my reels to be salt reels.  None get shielded spool bearings, but those aimed at salt get salt-resistant unshielded spool bearings.  The way I look at shielded bearings, salt water in, steam out, salt concentrates behind the bearing shield.  With my salt-resistant unshielded bearings, I flush them every time I oil them. These are KTF spool bearings. 

The one thing you can't do anything about is cathodic coatings on magnets, and these need to be inspected and replaced when they show the beginning filiform corrosion.  This was after 4 years exclusive salt use.  Note that the corrosion products of metals in salt are more corrosive than the salt itself.  E.g., Ferric chloride and cupric chloride are strong acid oxidizers - if you see a rusty bearing, get it out of there, no cleaning will help. 

 

I tried full zirconia spool bearings in my surf reel, but couldn't stand the noise, and went back to MTCW spool bearings (the ZrO are in my back-up mono spools now). 

Fully sealed reels, Van Staal, IRT, are really for the surf, and then, primarily for the NE surf.  Sand slurry from the surf is a greater concern than salt.  Labyrinth seals, such as Shimano X-Protect are everything you need if you're not going to dunk your reel and leave it. 

 

Excellent info, I had a few saltwater low profiles+ conventionals but you are right the magnets rust sadly, and they seem to soak up salt in the internals much easier and need  a deep cleaning more frequently than spinning.If I may ask, one of my reels has double shielded bearings for salt, do they assist in saltwater resistance in comparison to standard freshwater bearings?

You definitely want shielded bearings in the drives of salt reels - Daiwa magseal, even better. 

Double shield - assumed metal and rubber, sounds like a step-up for salt drives. 

Salt exposure tends not to get deep in the drives unless you dunk the reel, and then you should probably take it down, clean, and re-lube. 

 

I've seen some posts of rusted bearings on FFR and trying to clean them - never do that. 

Anytime you see rust, Replace. 

22 minutes ago, bulldog1935 said:

You definitely want shielded bearings in the drives of salt reels - Daiwa magseal, even better. 

Double shield - assumed metal and rubber, sounds like a step-up for salt drives. 

Salt exposure tends not to get deep in the drives unless you dunk the reel, and then you should probably take it down, clean, and re-lube. 

 

I've seen some posts of rusted bearings on FFR and trying to clean them - never do that. 

Anytime you see rust, Replace. 

Excellent info, thanks!