1941 Zinc Chromate Color

L-4Pilot · **Joined:** Tue Jan 18, 2011 10:35 pm **Posts:** 616

This is a L-3 Aileron that has been in storage since the early 1950s. The cover is not factory original having been done after the war but the frame still has it's original factory Chromate which is a bright yellow green. Thought you would enjoy the photos. BTW, each rib lace was tied off individually which I found interesting.

quemerford · **Joined:** Tue Jun 17, 2014 4:19 pm **Posts:** 1595

Important to remember that zinc chromate isn't a 'color' as such, but a protective treatment. Hence the hue differs since it doesn't need to comply to FS regs.

L-4Pilot · **Joined:** Tue Jan 18, 2011 10:35 pm **Posts:** 616

The large sheets of aluminum were dipped and/or sprayed with the chromate and then stencils with the correct IDentification of aluminum type and hardness. The spar 17S would be 2017 in todays coding.

COMPARISON OF MODERN &
OLD SYSTEMS OF ALUMINUM ALLOY DESIGNATION
Although the old system of aluminum identification has been obsolete for many years, stock with the old markings is still occasionally found. The following comparison is presented as an aid in identifying such materials in terms of the modern system.

In the old system, alloy composition was indicated by a one- or two-digit number followed by the letter “S” to indicate that it was a wrought alloy, i.e., an alloy that could be shaped by rolling, drawing or forging. Any variation in the basic composition was indicated by a letter preceding the numerical alloy designation. For example, A17S was a modification of the basic alloy 17S. In modern terminology these two alloys are designated 2117S and 2017S, respectively. Temper was designated by a second letter: “O” for soft (annealed), “H”for strain hardness of non heat-treatable alloys, and “T”for hardness of heat-treatable alloys. Degree of hardness of non heat-treatable alloys was indicated by a fraction preceding the letter “H”. For example, 3S1/4H would be quarter-hard 3S alloy.

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1941 Zinc Chromate Color

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