OK guys, first of all when pasting from Word, first post to a text file, save and close it, re-open it and paste from it to avoid syntax errors, Now:
as mentioned before on this forum there are some reasonably inexpensive coatings that adhere reasonably well to metal sold by Brownells and others in a DYI format. But I¡¦m not writing about these today, because the directions for these are on the back of the can. Today I want to talk about the next step up ¡V sending your parts to get professionally finished. The first and most important question to ask is, why bother? Well, personally, my Russian heritage makes me genetically predisposed to Vodka and anything that makes a gun more rugged, reliable, and maintenance free. I did spend a lot of time in Texas growing up, so now I actually prefer Tequila, but my quest for more rugged guns continues. I have traveled for work from just south of Canada border to New Mexico for the past 3 years, and always at least one airgun has been with me. Needless to say I have done everything from dropping them in snow and mud to spilling pop on them, so I have no use for a pretty gun that won't hold up. For that reason I became very interested in making guns that can keep up with me. Now on steel, about the best thing that bluing can do for you is hide beginning of rust as it starts to eat your toys - it is not a terribly effective corrosion barrier. Bare aluminum surfaces tend to gall when in dynamic contact with other metal, and other metals like brass form oxide layers that only look good on roofs. So, with that in mind, here are some alternatives:
Quick interlude:
When I posted the inquiry on the yellow forum about whether I should get the info together for this post I got an e-mail from Matt, who, I'm sure, will chime in if he would like to. He offered his help with this post and I ran some drafts by him to make sure we didn¡¦t leave out any helpful information. Also he pointed to some more resources, and I have downloaded some PDF documents that basically go more in depth on the subject for this post. Shoot me an e-mail if you'd like a copy.
Anodizing:
This is, of course, a controlled generation of an Aluminum oxide layer (harder than just about anything other than Diamond and a few ceramics) on the surface of your part - basically a controlled corrosion process. After the porous oxide layer is formed the parts may be dyed in your color of choice, and the porous surface is then sealed (how I'm not sure). There are 2 commercial finishes Type 2 and type 3. For Type 2, or color anodizing, a 0.0005¨ to 0.001¨ layer is formed. Roughly half of this layer is below the original part surface and half is above it. Not being very thick this layer mainly serves an aesthetic function, as a tougher than paint color layer. It does protect against light abrasion, but deteriorates easily, especially around corners. Unless otherwise specified you can expect that the factory anodized aluminum part you have is Type 2. As of 2 years ago a now defunct outfit out of Fort Collins, CO charged me $40 to do a type 2 batch of 120 mixed size parts. Type 3 anodizing is a 0.0025¨ to 0.0035¨ wear resistant surface. Again, roughly half of it is above the original surface and half below. Make sure you account for the dimensional growth of the finished parts (like using oversized taps for threaded holes or masking the threads) before making them. The above mentioned outfit also charged me $60 for a type 3 mixed batch of 80 gun parts. Either of these finishes make your final product more professional looking, and, for me, are a requirement to consider the Aluminum part finished. Anodizing does have its problems. Aluminum Oxide is a type of ceramic, so it is very hard but very brittle which makes it chip when flexing. Also, if it does wear off between dynamic bearing surfaces it becomes an abrasive that accelerates part wear. Matt has pointed me to a Teflon impregnated Anodized finish with improved mechanical properties, but I haven't yet located a firearms oriented vendor. I do have some specs on this finish I can send you. Also, keep in mind that because this finish is hard but brittle it will chip easily from sharp parts corners. On sharp inside corners, blind and small holes finish thickness will also be reduced, because of poor solution circulation in these areas. Below are pictures of Crosman 7075 T6 AL Type 3 anodized breech prototypes I made. Note the radiused corners for increased strength and anodizing design considerations listed above.
Here Matt has some good info on anodizing:
"MIL-A-8625F defines the different types and classes of anodize the type specifies the basic process used to create the oxide layer. Type I specifies chromic acid anodize Type II specifies sulfuric acid anodize (most common as far as I know) Type III specifies hard anodic coatings (there are others but they are sub-sets of the above). The class indicates dyed or non dyed. Class 1 specifies non dyed Class 2 specifies dyed the mil spec does not define the type of electrolyte that is to be used for Type III. It says that any process that can provide a heavy, dense coating of the specified thickness can be used. It also indicates that Type III coatings should not to be applied to alloys with copper content over 5% or a silicon content over 8%. There is an abrasion resistance specified for Type III of 1.5mg/1000 cycles except for alloys with a copper content of 2% or higher. Then the spec is 3.5mg/1000 cycles. Due to the porous nature of anodize, Type I & Type II anodize are normally sealed to improve corrosion resistance. Sealing can be done with numerous solutions. In my experience boiling water and nickel acetate are common. Depending on what you want, corrosion resistance or abrasion resistance, Type III may or may not be sealed. Sealing is omitted for maximum abrasion resistance. If the best corrosion resistance [is desired] with Type III is obtained when it is sealed. Sealing solutions are similar to Type I & II. Parts will need to be racked for processing. Specifying appropriate racking areas ahead of time will help eliminate exposed racking marks or scratches from removal from racks. Racks are often made from titanium or aluminum and can damage. Aluminum racks have to be stripped on a regular basis due to anodize buildup. Typically I have used a total coating thickness of .0002" to .0005" for clear anodize. If this type of thickness is specified, oversize threads are not typically required. Even with thicker Type II dyed anodize we typically do not oversize threads. Small diameter and fine pitch threads would probably be oversized but we just don't do that very often. One of the critical things, especially for Type III (hard anodize) is to make sure the anodizer knows the alloy. The tank setup for 6061 is quite different that for 2024 or 7075, etc. Alloys with high copper contents are more difficult to hard anodize and can burn easily. Typically 2024 is limited to around .0017" total coating thickness for normal production. With special setup and electrolyte chemistry greater thicknesses can be generated but it is very uncommon in my experience. Hope this is helpful, Regards, Matt¡¨
Plating:
These processes deposit a layer of harder, more corrosion resistant metal on the surface of your part. In firearm applications thicknesses vary from 0.0002¨ to 0.0006¨. Depending on design specs, most of these finishes can be applied to just about any metal surface. One problem with any plating is that it retains a very high surface tension and tends to peel away from the part when scratched through. Thorough surface prep is key in any plating process. Also to reduce this tendency a thorough plating process will include post-plating heat treatment to relax the plating and improve its bond with the part. The heat treating may also be used to harden the finish but, of course, that may also affect any cold-worked properties of flexible parts like springs and parts made of nonferrous alloys. There are 2 general categories, Electroplating and Electroless plating. Basically, in electroplating one wire is connected to the part and one to a plating metal source. The 2 are submerged in an acid-ion solution and DC current is run through the wires. The plating metal atoms (ions) then dissolve in the acid and those in the solution deposit on the metal part. One of the disadvantages of this finish group is that the thickness of the plating depends on the electromagnetic field distribution on the surface of the part. It works fine for tubes, bars and other simple parts, but on every edge, step, or other change in geometry, electromagnetic field concentrations create a thicker finish deposition. Small holes may bridge off at the surface because of this issue. Also, Matt suggested I look into hydrogen embrittlement from electroplating. It turns out that the electrical current also breaks down the water molecules into oxygen and hydrogen. The free hydrogen penetrates the surface of the part, and acts like little microscopic wedges between the metal's grain boundaries. The surface of the part then becomes brittle. It is another problem that can be cured by heat treating the plated parts around 300 deg. F, which drives out the hydrogen atoms. Electroless plating eliminates the electrical current and deposits the finish through a chemical reaction between the plating ion solution and the part. The only commercial electroless finishes I am familiar with are nickel based. This family of finishes is not as resilient as some of the tougher electroplated finishes, however the depostition process results in a much more consistent plating layer, which allows for more precision. When purchasing a gun that has been finished at the factory it¡¦s important to make an effort to recognize what finish type is hiding behind a manufacturer¡¦s fancy "Super-Duper-Norust TM¨ brand name, because it will let you know what to expect. One of the advantages of choosing your own finish is QC under your control.
Electoplated Nickel (aka Nickel plating)
This is the oldest firearm bluing alternative - available on guns like S&W revolvers during the early 1900¡¦s (earliest that I know of). It is reasonably effective, and of course, very decorative. The problem is that when a scratch or wear expose the steel underneath, which is then exposed to sweat or other moisture, the electro-chemical interaction between the nickel and the steel accelerates the corrosion of the part. An airgun example of electroplated nickel is a Sheridan Silverstreak.
Hard Chrome Electroplating (aka hard chrome finish, matte chrome finish, or dense chrome)
This is great stuff, but it is getting harder and harder to find vendors, because of the very environmentally unfriendly chemicals involved. It's really too bad because hard chrome is probably the toughest plating for firearm applications. The most common place you¡¦ll find it is inside an AK-47 barrel. Need I say more? Well I suppose there is one more thing. When scratched or worn through the finish offers sacrificial anode protection to the exposed steel. Basically when exposed to moisture the chromium is more prone to corrode, which significantly cuts down on the corrosion of the steel. Of course, as with aluminum, chromium corrosion practically stops after forming a thin layer of oxide on the surface, so until that protective oxide layer is removed virtually no more corrosion takes place. This chemical interaction between chromium and iron is what makes stainless steel stainless, except the chromium is part of the alloy instead of just being on the surface. Matt also reminded me to mention the adhesion issues with plated finishes. Hard chrome has the strongest adhesion of all the finishes here. Basically, with proper prep and plating practices about the only way to remove the metal under the hard chrome plating is to corrode it away from under the chromium layer, or if it is mechanically sheared this finish will fail at the substrate metal not at the plating-substrate interface.
Electroless Nickel (aka E-Nickel)
This is a base for a range of finishes. Basic electroless nickel finishes are commonly found on lower end "all weather¨ muzzle-loaders. You can distinguish hard chrome from e-nickel in a side-by-side comparison by color. Chrome has a grey-silver color and e-nickel has a yellowish-silver color. They are quite effective and, unlike the electroplated nickel do not have the tendency to accelerate scratch corrosion. I'm really not sure why that is, because the nickel-steel cathode-anode couple still exists but somehow it is a more passive finish. Electroless finishes do not adhere as well as electroplated finishes, and surface prep will make or break their longevity. Because, unlike hard chrome, these finishes will fail at the finish-substrate interface, they are not used inside rifled firearms barrels. Airgun barrels are not subjected to the same stress levels, but you have to communicate with the vendor, as they will be inclined to mask the bore if they think it's for a firearm. The finish thickness is more uniform than with electroplated finishes, but whereas electroplating deposits more finish on sharp corners, electroless finishes deposit less, so again sharp corners should be eliminated whenever possible from your design - which is part of good fabrication practices anyway. Again blind and small holes will not plate well, so avoid them whenever possible. If you must have a blind hole, try to drill a small relief hole, if you can, to establish solution circulation through the cavity. The basic E-Nickel plating is relatively inexpensive too. The aforementioned and now defunct local vendor in Fort Collins plated a mixed 103 small parts batch for me for $150. There are some fancier upgrades in this finish group. One I'm fond of is brand named NP3. This is a mixture of Nickel and Teflon. While softer than straight E-Nickel, the Teflon reduces this finishe's friction coefficient and improves its corrosion resistance. It is probably only an attractive alternative to folks as crazy as me, because a batch of 62 (a couple of complete airgun¡¦s worth) mixed parts cost me around $300. If there is a gun you plan to keep for the rest of your life (like an R1 he he he) that sort of an investment is negligible. Esthetically I find this the most attractive finish. Its dark grey color very much resembles Ruger's "target grey" nickel plated (don't know what process) stainless guns. The first picture below is of a couple of 22XX guns I put together with E-Nickel plating. Next one down is an NP3 plated CZ634, R1, and the bottom picture is an NP3 plated AL Logun Axsor breech.
Here Matt has some good info on metal plating:
"As for adhesion issues with electroless coatings...you are correct, surface prep is critical to good adhesion but even with good surface prep they will not adhere as well as an electroplated equivalent. Hard chrome has very good adhesion when compared to electroless nickel, and thin dense chrome has excellent adhesion. With thin dense chrome, the substrate often has to fail for the coating to come off. There is some good info at
http://www.nimet.com/engineering.php" target="_new" rel="nofollow">http://www.nimet.com/engineering.php>; (you have to register) that talks about electroles nickel buildup around edges and into holes. Another issue for electroplating is the possibility of hydrogen embrittlement. During the electroplating process hydrogen is generated and can be absorbed by the steel. Basically the hydrogen starts to collect in tiny voids along grain boundaries. As it collects in the void and creates internal pressure. This can lead to reduced ductility and can cause failure under very low loads. High strength steel alloys are the most sensitive to hydrogen embrittlement but it is possible with many materials. A post plating bake is normally used to drive the hydrogen out, thereby restoring the tensile properties. The bake temperature has to be lower than the tempering temperature so that the hardness and therefore strength is not changed. 375 to 400F is fairly common. Fasteners are common victims of hydrogen embrittlement."
Epoxy/molybdenum based finishes
These are epoxy based finishes that are sprayed on and baked at around 300 F to cure. What makes them neat is that the molybdenum particles suspended in the finish make it very tough, so you can make it thin - I think as thin as 0.00025" to 0.00015". Because the epoxy has a lower modulus of elasticity (more flexible) than the metal part it will not crack if the metal flexes. It is a less resilient finish than plating or type 3 anodizing, but it is very corrosion resistant and not terribly expensive. Also some less desirable alloys, like zinc and 3000 series extruded AL alloys used in trigger guards and other airgun components do best with this finish, because they are so soft that they don¡¦t hold on to the harder less flexible finishes very well. Also, these finishes have a range of colors to choose from for the fashionably inclined. I have had some R1 trigger guards refinished in black "Roguard", which is Robar"s version of this finish type.
Phosphate
I don't know much about this finish except that it's reasonably tough, retains oil quite well, but doesen't work great between moving surfaces because it results in a higher friction level between parts (my practical personal experience with this finish was on a post-war P38 and an A1 M16), and, like epoxy based finishes, is not applied inside barrel bores. I suspect this finish may soon be replaced with the epoxy finishes in firearm applications. I know that many grade 8 bolts are phosphate coated, and I don¡¦t know if there is any difference between that finish and what I have seen on the guns. It does form a stronger bond with metal, so some military weapons use a phosphate base, and an epoxy or epoxy/moly topcoat for a very robust combination finish. I've looked into that combination, but my favorite NP3 finish still turns out cheaper, so I'm sticking with it.
Some helpful hints:
1. Find out and/or specify your finish thickness.
2. Do not plate pins if you plate the parts (ie trigger housing pins break-barrel pivot bolts etc.) they go into.
3. Make sure you do not have any tight threads (mostly an issue with type 3 anodizing)
4. Now, lets do some quick math: Let's say you want to plate a barrel band and a barrel for a gun. The clearance between these parts is 0.002¨. Finish thickness is 0.0004¨ to 0.0006¨ per surface. Will the finished barrel fit through the finished barrel band? Not likely. With a finish thickness of 0.0006¨ the ID of the band will decrease by 0.0012¨ - say from 0.438¨ to 0.4368¨, and the barrel OD will grow by 0.0012¨ - say from 0.436¨ to 0.4372¨. See the problem? Tiny numbers are a huge pain in my butt. Don't worry though, it only takes a couple times of paying a couple of bills for a strip and refinish to never make that mistake again.
5. Make sure everything is deburred, bead blasted, honed etc. before you send off your parts. If you miss something you wanted to do beforehand you will definitely find it after the fact.
6. If you want barrel bores plated make sure you discuss it with the vendor first and note it on your order.
7. Lots of things, like muzzle brakes, on airguns are attached with lock-tite - make sure to take these apart and clean out the locktite before sending your gun parts off.
8. You probably will not be able to find a vendor for anodizing aluminum parts with permanently attached steel components, because the steel will contaminate their anodizing tanks.
9. Some things that Matt reminded me to emphasize: Remember sharp corners and blind or small holes will not have the finish consistency of the rest of the part, (As you have read the reasons differ, but the result is always inconsistency) so try to reduce them in your design.
10. Sending parts instead of an assembled gun puts QC into your hands. This is YOUR gun so YOU should be the best and toughest QC inspector of the work performed on it. That¡¦s the whole point of this exercise.
11. Reading this post will not make you refinishing guru, so do some research on your own after you read it and then learn the best way ¡V practice.
Placing your order:
Make sure you package everything thoroughly. There¡¦s nothing worse than getting back parts that got scratched by each other during shipping and were subsequently plated. It really hurts. Usually, I call ahead and discuss with the vendor what I¡¦d like to accomplish, get input from him, and get ready to ship. Then I take a picture of all the parts I¡¦m sending, number them, and write up a brief description of what I¡¦d like. Mr. FedEx then speeds of, and in 1 to 2 months I get a healthy bill and once I pay it I get my parts back. Here is an example:
To:
The Robar Companies, Inc.
21438 North 7th Ave,Suite B
Phoenix, Arizona 85027
(623) 581-2648From:
Dmitry Smushkov
Dair Designs
XXXX Yxyyx St.
Fort Collins, CO 805XX
Phone: (XYX) XYZ-3851
Dear Robar Representative,
First of all thanks for the good job on plating the last batch of parts. This is another batch (batch #4) for NP3 plating. As usual I have included a picture of all parts for your reference. OK, so here is the rundown of special requests/instructions:
„X This batch has no firearm receivers, so I wonder if you could save me on shipping and not ship it back by 2nd day shipment.
„X There are no critical tolerances, so please plate on the heavy side: 0.0005¨ to 0.0006¨.
„X All barrels are airgun barrels, so please do not plug the bores for plating. The plated bores turned out quite well last time, and I would like the corrosion resistance this finish offers in the bore.
„X Parts 1 and 2
o Parts 1 and 2 are rework from last shipment. It turns out they were locktighed or epoxied together and came apart as soon as I took them out of the box.
„X Parts 3 - 7
o Parts 3 - 7 are Aluminum and will need to be stripped of their anodized finish.
o I spoke with Karl before sending them and he said there shouldn't be any problems NP3 plating them.
o Part 3 has a steel part peened in, which, according to Karl should be OK.
„X Parts 8 and 9 are Zinc die cast trigger guards. I hope you'll be able to NP3 plate them.
o If you cannot NP3 plate these 2 and it would be the same price or cheaper to coat them with dark green or black Rogard go ahead and apply the Rogard finish at this time.
„X Part 10 is not a spring, so the plating process should not cause problems.
o It attaches in the back of the magazine well on a CZ 75 and protects the hammer spring from dirt etc.
„X Part 11 is a hammer assembly with pins peened in place.
o If you can disassemble and reassemble it please do so, otherwise plating it as an assembly is fine by me.
„X Part 12 is a riveted barrel assembly. Plate as an assembly.
o I understand that the internal surfaces of the riveted joint will not get plated.
Thanks for your help, and I'm looking forward to sending you a bunch more work in the future.
Dmitry Smushkov
Websites for finish vendors
The one I have used extensively is Robar. They do a great job prepping parts and I really enjoy signing over my paychecks to them. I'm going to have to try an anodizing outfit as well though, because my local guys are, sadly, out of business. Some of these vendors I have stumbled upon myself and some, including Robar, were recommended by other forum folk.
http://www.mrarms.com/index.html" target="_new" rel="nofollow">http://www.mrarms.com/index.html>;
http://www.eabco.com/cssfg.html" target="_new" rel="nofollow">http://www.eabco.com/cssfg.html>;
http://www.shootersolutions.com/allproducts.html" target="_new" rel="nofollow">http://www.shootersolutions.com/allproducts.html>;
http://www.hotflashrefinishing.com/" target="_new" rel="nofollow">http://www.hotflashrefinishing.com/>;
www.originalmetaloy.com
http://www.robarguns.com/DesktopDefault.aspx?tabid=4&tabindex=2" target="_new" rel="nofollow">http://www.robarguns.com/DesktopDefault.aspx?tabid=4&tabindex=2>;
http://www.techplate.com" target="_new" rel="nofollow">http://www.techplate.com>;
The website Matt recommended, which has awesome info but you have to register:
http://www.nimet.com/engineering.php?action=signup" target="_new" rel="nofollow">http://www.nimet.com/engineering.php?action=signup>;
I hope this helps you guys. I'll be happy to help you in any way I can if you decide to attempt this. Just shoot me an e-mail and I'll be happy to give you my number, so we can chat about all this stuff. I'll check on the post in a couple of hours and edit any characters that were screwed up because of paste from Word. Good luck and remember a hungry airgun is a sad airgun, so be sure to feed yours regularly. I will continue to edit out distracting paste errors. Later, D
Steve
Yellow Forums Administrator
http://www.yellowforum.com
http://www.airgunforum1.com
"Our unity is our strength."
