- Moderator
- #161
Jeff Kilgroe
Well-known member
All context aside -- we have obviously thrown it out the window at this point. The original statement made about titanium and tap water was misleading. It is analogous to saying, "OMG! We can't use steel for a mount because it rusts when exposed to tap water!"
Like steel, there are a multitude to titanium alloys, some of them fall into the realm of "stainless" and corrosion resistant -- US military and aviation spec CRES rating territory. Titanium still remains as one of the most corrosion-resistant elements known. If you want a truly corrosion-free mount and camera body for your Epic, give RED a call and see if they can make you a special one out of an 8K gold with 440C stainless steel mix. It still would be a bit soft for the mount I think, but damn that camera body would shine and would never tarnish, rust or corrode, ever. Have them cut the buttons out of diamonds while we're at it and have the lenses coated with micro-form sapphire crystals.
It's good to see you have some backup for your statement. However, there are a multitude of titanium alloys and compounds. Not as many out there as steel variants, but quite numerous. Some are susceptible to certain types of corrosion, others are not but at the same time vulnerable to other types. Re: sources. I have access to your #1 and #2. #1 has a lot of info and still does not even begin to dig into a fraction of all the possible alloy compounds. #2 only talks about one alloy -- Titanium with 6% aluminum and 4% vanadium and, yep, it corrodes a bit. Not much more than than most common forms of stainless steel will under the same conditions if you really want to analyze it. Here are two good data sheets for Ti-6Al-4V. FWIW, most of the "stainless" or CRES rated Ti alloys are not transitional alloys such as this, but are beta stage alloys. Often containing Chromium, Zirconium, Molybdenum and even gold. Titanium loves to combine with hydrogen and it can be a problem in certain production methods, one of the worst being cooling welds and it's often considered better to cool welding of titanium with certain types of oils as opposed to using water. Titanium likes to combine with hydrogen loosely, which actually makes it ideal for some applications -- such as hydride mixture and hydrogen storage industries.
ti-6al-4v:
http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641
http://cartech.ides.com/datasheet.aspx?i=101&E=269
Tap water is indeed highly corrosive and has cumulative effects on aluminum and stainless steel as well. Fluoride, chlorine, copper, sodium, etc.. are all commonly found -- often as specific additives -- in tap water.
Talking about the SR-71 is a specialized case. I don't believe Lockheed or the USAF has ever made it public as to which alloys were specifically used for structural components or the titanium skin. If I'm not mistaken, the skin has high percentages of molybdenum and chromium, relative to more commonly used alloys. We also have to sprinkle it with a good amount of military paranoia -- someone points out a potential issue and they take their efforts to the nines in avoiding it. Lockheed chose titanium not only for its strength to weight ratio, but also its resiliency to corrosion. Many surfaces on the SR-71 take super-sonic impact from raindrops and cloud moisture during flight and instantly boil / vaporize this water (complete with impurities) on contact. Rain water is hardly pure and in many cases is just as impure and corrosive as common tap water, or more so as it often has high concentrations of sulfer, carbon dioxide and even ammonia compounds.
Of course. And we don't know what RED has chosen. Off the top of my head, there are a couple common alloys I would consider using. And a few of them are completely inert in common tap-water, even over time, as they are inert to chlorine, bromides, sulfur and sodium compounds.
The point is, we have to look at individual alloy compounds. Many titanium alloy components for SCUBA gear are made from TI-8Al-3V-3Cr for clips and buckles, dive computer and watch housings. TI-2C-3Fe-4Cr-6V is a common one for dive knives as it is even more resistant and holds an edge. It can be polished and looks almost like silver when it is, you'll find it on watch bezels sometimes, but it's very hard to work with and it can be heat-tempered or cold-tempered for hardening.
There are lots of undocumented Ti alloys out there, lots of research currently going on in this area as Titanium is becoming more and more viable for use in precision milling applications and metal fabrication. I know of one manufacturer that is trying to bring to market a titanium alloy to replace certain types of common sheet-metal used for roofing and gutters. It's an alloy made of about 35% titanium.
Titanium and most of its common alloys are one of the few metals that can have corrosive properties altered through molecular alignment or tempering.
Lockheed observed over the service of the SR-71 that the titanium skin would continue to harden from the high heat it was exposed to during supersonic flight and after enough time, it became difficult to even get their intended paints and coatings to adhere to the skin.
Like steel, there are a multitude to titanium alloys, some of them fall into the realm of "stainless" and corrosion resistant -- US military and aviation spec CRES rating territory. Titanium still remains as one of the most corrosion-resistant elements known. If you want a truly corrosion-free mount and camera body for your Epic, give RED a call and see if they can make you a special one out of an 8K gold with 440C stainless steel mix. It still would be a bit soft for the mount I think, but damn that camera body would shine and would never tarnish, rust or corrode, ever. Have them cut the buttons out of diamonds while we're at it and have the lenses coated with micro-form sapphire crystals.
It's good to see you have some backup for your statement. However, there are a multitude of titanium alloys and compounds. Not as many out there as steel variants, but quite numerous. Some are susceptible to certain types of corrosion, others are not but at the same time vulnerable to other types. Re: sources. I have access to your #1 and #2. #1 has a lot of info and still does not even begin to dig into a fraction of all the possible alloy compounds. #2 only talks about one alloy -- Titanium with 6% aluminum and 4% vanadium and, yep, it corrodes a bit. Not much more than than most common forms of stainless steel will under the same conditions if you really want to analyze it. Here are two good data sheets for Ti-6Al-4V. FWIW, most of the "stainless" or CRES rated Ti alloys are not transitional alloys such as this, but are beta stage alloys. Often containing Chromium, Zirconium, Molybdenum and even gold. Titanium loves to combine with hydrogen and it can be a problem in certain production methods, one of the worst being cooling welds and it's often considered better to cool welding of titanium with certain types of oils as opposed to using water. Titanium likes to combine with hydrogen loosely, which actually makes it ideal for some applications -- such as hydride mixture and hydrogen storage industries.
ti-6al-4v:
http://asm.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641
http://cartech.ides.com/datasheet.aspx?i=101&E=269
Tap water is indeed highly corrosive and has cumulative effects on aluminum and stainless steel as well. Fluoride, chlorine, copper, sodium, etc.. are all commonly found -- often as specific additives -- in tap water.
Talking about the SR-71 is a specialized case. I don't believe Lockheed or the USAF has ever made it public as to which alloys were specifically used for structural components or the titanium skin. If I'm not mistaken, the skin has high percentages of molybdenum and chromium, relative to more commonly used alloys. We also have to sprinkle it with a good amount of military paranoia -- someone points out a potential issue and they take their efforts to the nines in avoiding it. Lockheed chose titanium not only for its strength to weight ratio, but also its resiliency to corrosion. Many surfaces on the SR-71 take super-sonic impact from raindrops and cloud moisture during flight and instantly boil / vaporize this water (complete with impurities) on contact. Rain water is hardly pure and in many cases is just as impure and corrosive as common tap water, or more so as it often has high concentrations of sulfer, carbon dioxide and even ammonia compounds.
Of course. And we don't know what RED has chosen. Off the top of my head, there are a couple common alloys I would consider using. And a few of them are completely inert in common tap-water, even over time, as they are inert to chlorine, bromides, sulfur and sodium compounds.
The point is, we have to look at individual alloy compounds. Many titanium alloy components for SCUBA gear are made from TI-8Al-3V-3Cr for clips and buckles, dive computer and watch housings. TI-2C-3Fe-4Cr-6V is a common one for dive knives as it is even more resistant and holds an edge. It can be polished and looks almost like silver when it is, you'll find it on watch bezels sometimes, but it's very hard to work with and it can be heat-tempered or cold-tempered for hardening.
There are lots of undocumented Ti alloys out there, lots of research currently going on in this area as Titanium is becoming more and more viable for use in precision milling applications and metal fabrication. I know of one manufacturer that is trying to bring to market a titanium alloy to replace certain types of common sheet-metal used for roofing and gutters. It's an alloy made of about 35% titanium.
Titanium and most of its common alloys are one of the few metals that can have corrosive properties altered through molecular alignment or tempering.
Lockheed observed over the service of the SR-71 that the titanium skin would continue to harden from the high heat it was exposed to during supersonic flight and after enough time, it became difficult to even get their intended paints and coatings to adhere to the skin.
Last edited:
Or maybe that's what this RED thing has been about all along.
atriot:
.
