bead blast and corrosion

T

ThirdTooth

Joined
Mar 21, 2012
Messages
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a bead blasted finish has a substantial effect on a knifes corrosion resistance.
why?
explain this to me like I'm 8
thanks :)
 
Cause Mom said! :)

Bead blasting can create a micro textured surface and the little pockets that are formed make it easier for corrosion to begin when corrosive elements are left there. In contrast, a polished edge presents less opportunity for corrosion to start as well as making it easier to prevent. Think about wiping water off of a polished granite kitchen counter versus wiping water off a concrete driveway. Due to the textured surface, the bead blasting has also increased the total surface area of the blade exposed to corrosive element. Not all bead blasting is the same, however. Some bead blasting is in reality sandblasting, which really scores the surface of the steel. Glass bead blasting it is argued will only remove corrosion and not make the steel more susceptable to corrosion because it does not score the surface.

I wipe all my blades down with Marine Tuf-Cloth whether they are bead blasted carbon steel or polished stainless and never have any corrosion issues.
 
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Brisket said:
Bead blasting can does create a micro textured surface and the little pockets that are formed make it easier for corrosion to begin when corrosive elements are left there.
Click to expand...

Fixed that for ya, no offense. The rest of your post is mostly right on. Standard blasting processes will increase the likelihood of corrosion to some degree, regardless of the media used.

The only exception I know of is shot-peening, where the steel has to be finished to a high polish beforehand and the peening process lessens glare for a nice clean "frosty" look without tearing into the surface. It looks awesome, but it's pricy.
 
Attached is a photo of my old EDI Genesis II, with bead blasted ATS34 steel. This was my EDC for awhile. I like the shape and most characteristics of the knife, except for the bead blasted finish. I don't particularly care for stonewashed finishes either. I prefer a standard satin (machined) finish. In the photo you can see the staining/corrosion of this blade. I was able to clean the corrosion off a little bit but not completely. also it seems to me that a blasted finish would be more susceptible to showing scratches than a satin finish.

DSC_6670b.jpg
 
I had a Gerber Gator with an ATS-34 blade that had a bead blast finish and it would show specks of rust just from washing and not drying it.
Plus, no one my be a member and post under the age of 13. It's in the rules. DM
 
To simplify what bead blasting does, you're creating lots of small pockets in the surface. An analogy (somewhat crude) of what happens is imagine a crinkle cut potato chip of a certain size and a normal non-crinkle cut chip which has the same sized sihouette. If you "un-crinkle" the first chip you'll find that it's a lot larger than the second chip. If you think of the amount of salt you can put on a chip to season it as the amount of sites in which steel can corrode, the crinkle cut chip has a lot more surface area for which it can be salted so like bead blasted steel, if you were to measure the amount of surface area on the steel compared to the same blade with a mirror polish, you could similarly "uncrinkle" all the micro-pockets on the bead blasted steel and you'd realise that there is a lot larger surface area for which corrosion can occur. Hope it helps a bit haha, I know the chip analogy is quite hilarious xD
 
Blasting can be bad for a finish, but it has advantages also. A lot depends on the media used. Aggresive compounds like oxides etch deeply, removing a lot of material. Glass beads peen the surface more than they etch it and don't cause near the rust problems afterwards. But if you're putting a coat of finish over the metal you probably want the etch to insure it bonds tightly.

One thing about blasting, it's still the best rust removal method I know of. Blast, then polish. That gives a nice finish.
 
this is kind of in the same vein
I heard that an acid wash will do wonders for mitigating corrosion. but wouldn't acid eat away unevenly on a micro level causing the same issue and actually making it worse for corrosion resistance?
 
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