Bead-blasted blades & Corrosion Resistance

J

James Y

Joined
Feb 18, 1999
Messages
6,504
In general, bead-blasted blades tend to corrode more easily, but I have heard some bead-blasted blades (Outdoor Edge Magna, etc.) can resist rusting very well. Is that due to the smoother bead-blast finish, the type of steel used (AUS-8), or a combination of those?

How do the CRKT bead-blasted blades hold up under outdoor or wet conditions? I do own an M-16, but have yet to use it under corrosive type conditions.

Any feedback is appriciated.
Jim
 
Bead blasting effectively increases the surface area of the knife, making the knife more vulnerable to rust and corrosion. The light the bead blasting the lighter the effect. A steel which has more rust resistance to start - say 440C - is a better candidate than say A2 or O1 steels which rust rather easily.

I've started coating the blade of any knives I bead blast with paste wax and polishing with a soft cloth. The wax seems to protect the blade better than oil but must still be re-applied.

------------------
Totally new website!
http://www.wilkins-knives.com
 
In the metal industry all of the stainless houses constantly inform customers that polishing improves stain resistance, the higher the polish the greater the stain resistance. The explanation given is that polishing eliminates crevices and pockets where corrosive materials like de ionized water(rain)can remain trapped and begin to corrode the metal.

Bead blasting creates the conditions that polishing is intended to prevent so in theory bead blasted blades will corrode more readily than mirror polished blades.


------------------
george
www.tichbourneknives.com
sales@tichbourneknives.com


 
Hmmm... I' ve posed this same question before. And it seems that there are differences of experience/ opinions here. Some time back I believe it was Kit Carson, IIRC, who stated that a blasted finish actually helps to increase resistance to corrosion. It is possible that a glass bead and a sand blast yields a different effect. The glass actually peens the metals surface while the sand "scores" it. Am I making sense?

L8r,
Nakano
 
Nakano, most likely Kit meant that the coating that comes on as a result of his bead blasting helps protect the blade. Also, 440 series of steels has more resistance to rusting than say ATS-34 because of the chrome within the steel.

All steels are porous(you can call it grainy or whatever you like) at the microscopic level. This means that moisture will make it into all of them. To protect the steels many people put a barrier that has a much lower porosity than the steel and inhibits moisture from making it past these barriers. Teflon coatings are well known for this. Hard chrome is used for this to a much lesser extent since it is not much less porous than regular steel. Polishing reduces the microscopic surface area of the steel and ,thereby, reduces the amount of moisture that will make it through the steels surface. It will still rust, but it will take longer to do so. Forging also helps slow moisture from getting into the steel by aligning and compacting the surface grains increasing the surface density of the steel, thereby, making it much less porous.
 
Nakano2 and Cobalt have sort of got the general idea. From what I understand, there are 2 basic types of "bead" blasting. The final surface effect looks very similar, so they have been confused.

The "real" bead-blast uses various types of beads. Either glass beads, or steel ball bearings. Blasting with this type of bead has an effect similar to cold forging. It stress hardens the surface of the blade and aligns the grains of the steel, thus sealing the surface.

The other type of bead blasting uses sand grains. Sand grains are sharp and will score the surface of the blade. Although the final surface finish looks the same, it is actually closer to putting thousands of tiny scratches in to the surface. Thus instead of sealing up the surface, it opens it up.

The sad thing is that sand blasting is apparently cheaper and easier to do, and the equipment easier to get, so you're going to find more sand blasted blades than real bead blasted blades, and that's going to perpetuate the idea that bead blasting is bad, when actually, it's sand blasting that is at fault.
 
Steelwolf, Nakano2, Cobalt....
You are perfectly right:
real beadblasting compacts the surface and reduces tendency to rust, while
"sandblasting" (usind sharp cornered grit) greatly increases tendency to corrode.
Valid for any steel.
Taking a 10x loupe will generally show the difference. "Good houses" do not cheat....
smile.gif


------------------
D.T. UTZINGER

[This message has been edited by ZUT&ZUT (edited 04-15-2000).]
 
My CRKT M-16 corrodes very easily. But TuffClothing or oiling protects it. Bead blasted blades require constant care.

Kris
 
I use ATS-34 exclusively (with rare exceptions). I also use a blasted finish on more than 90% of my knives. I have not had any complaints of my knives (made from ATS-34) rusting. I believe that this has to do with several factors. #1 factor is the hardness of the blade. Blades that are not as hard will rust faster. Factory knives tend to be softer.

------------------
Lynn Griffith-Knifemaker

Now accepting Credit Cards

griffithknives.com
GriffithKN@aol.com
Griffith Knives Forum
 
I bead blast with a ceramic bead. It peens the surface, rather than cut it. Those who have seen this finish remark how smooth it is. The blade has to go to a 400-500 grit finish before it can be done. I will not hide any flaws or bad grind lines. If I'm powder coating, I have to use glass bead. The coating won't stick to the ceramic finish very well since it's so smooth.

Glass bead will shatter after a couple cycles thru the blaster and end up like sand blasting, cutting the surface and leaving it exposed.

I even use the ceramic bead on D2 with good results.
 
It's due to the type of steel. Since bead blasting helps retain moisture on the surface of the steel, it accelerates corrosion. If the steel is more corrosion resistant (more chromium usually) then the effect is diminished. Take care.

------------------
Fred
Knife Outlet
http://www.knifeoutlet.com
 
Kit, so would it be correct to say that ceramic bead blasting peens(or indents) and light polishes at the same time? Do the ceramic beads leave a ceramic coating on the blade or not?

The only bead blasting I'm familiar with is the type used to remove surface coatings from aircraft, and these are not true ceramic, but more of a plastic pellet. Certainly not harder than steel like the ceramic beads you are probably using.
 
I was wondering about Chris Reeves stonewashing his blades.How does this affect corrosion resisance? BTW I like the looks of it a lot better then bead or sand blasting.It also feels a lot smoother.
 
Rust resistance depends (among more things) on the presence of chromium on the very surface of the steel and on it's "status".
Whatever you do to the surface, at the end you should try to passivate it, i.e. slightly oxydize the surface chromium. An alkaline solution tends to do so, better are oxydizing agents, like nitric acid or hydrogen peroxyde (conc).
"scratching" does exactly the opposite, it takes away any passivated layer....
 
I once read a section on this topic on the KnifeArt Forum. As someone mentioned above, bead blasting makes the blade more porous (not sure of spelling). This will inherently make the blade more susceptible to rust, however, it is a double edged sword so to speak.

Since the metal is more pourous, it will therefore absorb more oil if properly cared for. The result is that if the blade is cared for, it will be more rust resistant than a highly polished blade.

Matt
 
Using Sentry's Marine Tuf-Cloth will seriously reduce the increaced probability of the corrosion of bead blasted blades.

Ron@SOG
 
James:

The following is based upon a lot of personal experience with these knives:

CRKT M16series knives will corrode if not protected from normal body sweat during warm weather (and I am not abnormally corrosive to knives either). My customers use Tuf Cloth to prevent this with no problems yet. I Tuf Cloth all the CRKT M16's that leave my show table even if the customer does not purchase a Tuf Cloth.

Lynn Griffith and Kit Carson both have a superior bead blast which seem more durable and corrosion resistant than the Benchmade or CRKT bead blasts that I have experience with.

That said I did go to using Tuf Cloth on all my customs once I discovered it's great properties. Who wants to risk the welfare of a great custom knife by Lynn or Kit?

Hope this helps,

Kevin

------------------
Kevin Pensinger
The EDGE Equipment
sales@theedgeequipment.com

Contact The EDGE for your custom cutlery needs!
 
Wow, I didn't expect this thread to get as many responses or to touch on so many aspects of bead blasting/corrosion.

Thanks, all!
Jim
 
You must log in or register to reply here.
Back
Top