My first KTM --- what is the deal with all the corrosion on the fasteners?! --- Best replacement kit?

Wouldn’t be to concerned about it, previous owner probably washed and put away wet. We always air compressor ours off before putting them away. Be sure and check all your bolts. The euro bikes loose bolts like nobody’s business. Blue loctite is your friend. Buy a pack of Bolt or specbolt fasteners for your bike and change what concerns you. Then buy another one for a spare 😂. The diagnostic light popped out of my 22 Husky. Little super glue around the edge and pop it back in. Done. Congrats on the bike. 

I dry after washing with air or let bike sit in the sun. But yes, the plating on the Austrians bikes is below the Asian quality. I have read it is due to environmental issues with the plating process? Many parts from KTM come with new oem hardware. 

Specbolt Nickel Wurks come in Engine bolt kits and plastic fastener kits. I think Nickel plating is outlawed in Austria. When I lived close to the beach my raw pipe and stock KTM fasteners went through hell. 

Another vote for the Specbolt Nickel Works kits.

Something else you can do for all those small M6 bolts all over the place, is do a bunch of measuring and then get some of that import Ti hardware from Fleabay. I would not trust that quality for anything structural but for all those small little bolts, they will be fine. A little more expensive but they will look nice forever.

I’m not too far from you. I picked up my ‘16 350 in Nov, ‘15 from Fay Meyers. That’s what mine looked like brand new and still look like currently. I have only had one problem with bolts(upper subframe, called for loctite, not sure if I put it on or not) in the 8 years of owning the bike. Spoke nipples are a completely different story though. 

BOLT brand makes a set of excellent sprocket bolts with the Japanese "Fuji" style lock-nuts in 12mm hex instead of 13mm.

I blue lock-tited the shifter bolt, upper/rear engine hanger bolts that go into the frame and the four subframe bolts before I even heard my bike run.   So far, zero issues with lost fasteners.

I run a small dehumidifier unit in my machine shop where the bikes live and WD-40 all my chains after washing bikes.   So far no rusty bolts in 12.1 engine hours on the bike I bought in August, 2023.

I second the point about spoke nipples.   I have one spoke nipple next to the rim-lock that completely unthreads every time I ride the bike.   KTM rims are butter soft and the spoke nipples are shockingly terrible.

Every bike has its negative points...

I think it’s soft wheels with pressure applied from the rim locks. The spoke nipples don’t back off but they get loose. I believe it’s the wheels causing the problems. Hit them with a torque wrench every couple engine hours, they usually set in around 30-50 hours. You can get some decent movement the first 10-15 hours but after that it’s usually 1/4ish turn for the 3 on either side of the rim lock. 

I've been hoping the one problematic nipple will settle in as @Splat03 mentioned in his post.

Ultimately, I plan to build a set of wheels on some OE hubs with better rims and spokes.
 

DID-STX rims and bulldog spokes.  Been down this path.  This is the way.   

Funny hearing about the corrosion.  I leave my 2-stroke pipes totally bare and they look exactly the same 1 day later.. or 1 year later.   Also have frequent bloody nose....  Pros and Cons....

I've gotten flamed on here for voicing my concern over the same topic with the fasteners.

I have a w9 rear wheel on my 2020 450 with the same problem, the nipple closest to the rim lock is always loose.  

BTW, for odd replacement bolt, check your local Ace Hardware. If it's like the one near my house, they have a shockingly decent supply of metric hardware, including some stainless.

Great info above. I’d just add to pull your seat every time you wash the bike and blow everything out. Water sits in all those pockets and rusts/corrodes everything because it can’t drain. Dust and dirt also settles there.