Blancoalex
Well-Known Member
Looking for NON Cerakote or Duracoat ways to finish/seal a stainless steel barrel after sandblasting for matte finsh. It is my understanding that it starts to oxidize and rust shortly after blasting. Thanks
Sandblasted SS treatment afterwards??
- Thread starter Blancoalex
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eklarsen
Well-Known Member
I've have many bead blasted stainless barrels, I haven't had any rust
david g ranes
Well-Known Member
have a hart barrel I had them bead blast looks as good as when they done it had it done in 2010. David
Blancoalex
Well-Known Member
Assume you are talking about glass beads! What is bead size ?
Depends on what you blast it with. If you used virgin media you would be fine. If the media you used had just blasted the rust off of some 50 year old farm equipment, it will transfer into the stainless and can cause a small amount of surface rust.
eklarsen
Well-Known Member
Never met her but I will take your word.
Dr. Vette
Well-Known Member
As noted, you have to use glass beads that have not been used for regular steel. Brownells sells some listed as "270+" grit which will work fine.
I've had a couple done by gunsmiths this way and they look great even years later. Use the right media and the right conditions and no rust will appear.
I've had a couple done by gunsmiths this way and they look great even years later. Use the right media and the right conditions and no rust will appear.
YES all Stainless Steel "rust" . Its called pacification, its the ability of most stainless steels to 'oxidize' aka rust as you say to create a surface barrier to prevent corrosion . There are issues as which alloy is being used as most American barrels are 416R and some Europeans use 17-4 PH . I've seen Howa , Remington and Tikka's with external pits on actions and barrels . What this means is the metal became contaminated with solvents or a combination of solvents an powder nitrates to form what appears to be a nitric solution which causes corrosion . Simple point if you use SS guns or barrels keep them clean of solvents and powder fouling and oiled . I work on a lot of suppressor fitted guns in NZ and you would not believe the degree of pitting I see when the suppressors are left on the barrels, many completely destroyed .
As pointed out contaminated blasting media with iron oxide-rust will show up later , quite correct.
As pointed out contaminated blasting media with iron oxide-rust will show up later , quite correct.
ntsqd
Well-Known Member
Assuming that the are no impinged iron particles in the surface of the SS the chromium in the alloy will do what it does on car bumpers, form an invisible oxide layer that seals the surface to further corrosion.
When SS is machined iron gets impinged. Doesn't seem to matter that only carbide tooling and no steel tooling was used in the machining of it, given the opportunity it will rust at least a little. I once cleaned a SS Mini-14 that was used on a commercial fishing boat. It was a nasty, pitted mess from all of the blood that got on it and wasn't cleaned off, even on the surfaces that were as-cast unmachined SS. Blood is a "super-oxidizer".
The way to remove those impinged iron particles is a process called "Passivation" and it employs varitaions on a nitric acid bath to remove the iron from the surface. In the process the surface has a similar invisible layer formed on it that seals the metal from further corrosion. Attached is the old US MIL-Spec for this process.
EDIT: I should mention that passivation results in a surface finish that looks "frosted" in most cases.
When SS is machined iron gets impinged. Doesn't seem to matter that only carbide tooling and no steel tooling was used in the machining of it, given the opportunity it will rust at least a little. I once cleaned a SS Mini-14 that was used on a commercial fishing boat. It was a nasty, pitted mess from all of the blood that got on it and wasn't cleaned off, even on the surfaces that were as-cast unmachined SS. Blood is a "super-oxidizer".
The way to remove those impinged iron particles is a process called "Passivation" and it employs varitaions on a nitric acid bath to remove the iron from the surface. In the process the surface has a similar invisible layer formed on it that seals the metal from further corrosion. Attached is the old US MIL-Spec for this process.
EDIT: I should mention that passivation results in a surface finish that looks "frosted" in most cases.
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Stainless rusts because (1) it is in a corrosive environment or (2) it has surface contamination.
For a matte stainless finish, I used an AL oxide blasting media which gets it 100% flat. Then I spray glass beads with low pressure, just enough to knock down the rough surface and give it some more scratch resistance. This yields a flat glass bead look. Using glass beads on a smooth surface only makes it appear more shinny. Think faceted diamond but on a much smaller scale. In another life, I bead blasted nuts and bolts and they always come out shinny ready for zinc plating. Maybe a very large glass bead or maybe crushed glass would give a better matte finish.
For a matte stainless finish, I used an AL oxide blasting media which gets it 100% flat. Then I spray glass beads with low pressure, just enough to knock down the rough surface and give it some more scratch resistance. This yields a flat glass bead look. Using glass beads on a smooth surface only makes it appear more shinny. Think faceted diamond but on a much smaller scale. In another life, I bead blasted nuts and bolts and they always come out shinny ready for zinc plating. Maybe a very large glass bead or maybe crushed glass would give a better matte finish.
There is one thing I don't like about bead blasted barrels and it has nothing to do with rust. If you ever rub your barrel on a cattle gate or some other hard surface, it will smooth the matte finish and stand out like a sore thumb. My guns are tools and get used as such, but it still is an eye sore to me. A polished barrel can be touched up easier IMO than a matted SS or CM barrel. It's just something to think about.
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Savage 22-243 AI
Well-Known Member
Never been a problem for me. I've had one bead blasted barrel since 1996. Used in prairie, rained on and not giving it much care on the outside. Other barrels are from 2006 or so. I do ceramic clear coat my CM barrels
