SR-71 Blackbird Mach 3 spy plane’s titanium parts made in summer corroded while those made in winter didn’t. Here’s why.

SR-71 Blackbird Mach 3 spy plane’s titanium parts made in summer corroded while those made in winter didn’t. Here’s why.

By Linda Sheffield Miller
Jun 15 2024
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The Blackbird

The SR-71, unofficially known as the “Blackbird,” was a long-range, Mach 3+, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft.

B-58 navigator recalls dropping Mark-53 nuclear bomb (without plutonium pit) while flying at 500 feet and at 628 knots, low level recce missions, dinner with Doolittle Raiders and Jimmy Stewart
CLICK HERE to see The Aviation Geek Club contributor Linda Sheffield’s T-shirt designs! Linda has a personal relationship with the SR-71 because her father Butch Sheffield flew the Blackbird from test flight in 1965 until 1973. Butch’s Granddaughter’s Lisa Burroughs and Susan Miller are graphic designers. They designed most of the merchandise that is for sale on Threadless. A percentage of the profits go to Flight Test Museum at Edwards Air Force Base. This nonprofit charity is personal to the Sheffield family because they are raising money to house SR-71, #955. This was the first Blackbird that Butch Sheffield flew on Oct. 4, 1965.

The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966.

The Blackbird was in a different category from anything that had come before. “Everything had to be invented. Everything,” Skunk Works legendary aircraft designer Kelly Johnson recalled in an interesting article appeared on Lockheed Martin website.

SR-71 art
This print is available in multiple sizes from AircraftProfilePrints.com – CLICK HERE TO GET YOURS.  Dawn at 80.000ft – SR-71 Blackbird

Production of the SR-71 was done at the Skunk Works plant, in Burbank, California, as the photos in this post show [the image were taken in 1965 and show some of the first SR-71 under construction: featured in the pictures are the first B models (957 and 956) under construction with an A-model (955). My dad Richard “Butch“ Sheffield told me that he watched these airplanes under construction at the Skunk Works plant at Burbank].

SR-71 airframes built almost entirely of titanium

The airframes were built almost entirely of titanium and other exotic alloys to withstand heat generated by sustained high-speed flight: in fact, the Blackbirds were designed to cruise at Mach 3 continuously for more than one hour at altitudes up to 85,000 feet.

SR-71 Blackbird Mach 3 spy plane’s titanium parts made in summer corroded while those made in winter didn’t. Here’s why.
The #957 under construction You can see the raised canopy. This aircraft crashed at Beale Air Force Base in 1968.

Blackbird’s engineers had a perplexing problem as to why some of the titanium was corroding. However, they figured out the reason. It was chlorine in the water!

According to Wisconsin Metal Tech, the engineers of the SR-71 were among the first people in history to make real use of the material. In that process, they ended up throwing away a lot of material, some through necessity, some through error. At times the engineers were perplexed as to what was causing problems, but thankfully they documented and cataloged everything, which helped find trends in their failures.

Spot welded parts made in summer corroded while those made in winter didn’t

Blackbird production
It was important to put US Air Force on the airplanes just in case they were flown over or near hostile countries if there was no identification on the airplane they would be considered spies and would be shot. The trainer models never left the US. Nevertheless they were marked just in case they had to leave the US.

They discovered that spot welded parts made in the summer were failing very early in their life, but those welded in winter were fine. They eventually tracked the problem to the fact that the Burbank water treatment facility was adding chlorine to the water they used to clean the parts to prevent algae blooms in summer, but took it out in winter. Chlorine reacts with titanium, so they began using distilled water from this point on.

They discovered that their cadmium plated tools were leaving trace amounts of cadmium on bolts, which would cause galvanic corrosion and cause the bolts to fail. This discovery led to all cadmium tools to be removed from the workshop.

Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Twitter X Page Habubrats SR-71 and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.

Cool Video Explains how SR-71 Blackbird’s J58 Turbo-Ramjet Engine Works
This model is available in multiple sizes from AirModels – CLICK HERE TO GET YOURS.

Lockheed photos via Tony Landis and CIA


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Linda Sheffield Miller

Linda Sheffield Miller

Grew up at Beale Air Force Base, California. I am a Habubrat. Graduated from North Dakota State University. Former Public School Substitute Teacher, (all subjects all grades). Member of the DAR (Daughters of the Revolutionary War). I am interested in History, especially the history of SR-71. Married, Mother of three wonderful daughters and four extremely handsome grandsons. I live near Washington, DC.
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