What was the purpose of putting lead in gasoline? Did it reduce “knocking” or “dieseling”? What was its role in paints?
- Jinx
Word on the street from the old guys who remember when my 65 Lincoln was new, the lead in fuel acted as a lubricant for the top end of the engine (the valves, cams, heads, etc). The same guys also said that I should no use a lead additive because it was WORSE for the engine as a whole rather than having an underlubed topend that will probly have to be rebuilt before the lack of lead is an issue.
The question of lead in gasoline has been discussed here several times. Tetraethyl lead is an octane enhancer, and also acts as a lubricant.
Lead in paint was usually in the form of lead carbonate (“white lead”) which improved the wearing qualities of the paint and made white paint brilliantly white. Some other pigments also contained lead (read lead, blue lead, etc.)
The tetraethyl lead in gas also vaporized inside a car engine’s combustion chambers and coated the exhaust valves during the exhaust stroke. This kept the hot valves from sticking to their seats, which wore the valves and seats.
Red lead, or lead oxide, is a great corrosion inhibitor and was used in steel primers for that purpose until fairly recently.
Medium chrome yellow, which is mostly lead chromate, was used for years to make “construction yellow” paint (like the color of a yellow bulldozer) and yellow pavement striping paint. Medium chrome yellow and lead molybdate (“moly orange”) are still being used in some pavement striping materials (mainly because it’s hard to find a good substitute for it), but their days are probably numbered.
Another old use of lead in paint was in drying agents, which were lead salts of carboxylic acids (aka “lead soaps”) used to catalyze the drying reaction of oil paints.
It’s been less than 10 years since people quit using red lead and lead dryers, and white lead was taken out of U.S. house paints in about 1978. Even so, as far as I know, white lead is the biggest hazard of them all, in terms of the number of people that get poisoned by it.
My understanding of paint technology in the days before paint was widely commercially distributed was that lead was allowed to oxidize, which produced litharge (lead oxide). This was combined with an oil or varnish, typically linseed oil because it was cheap and widely available. Verious substances were then added to color the white paint base. Iron oxide --good old rust— produces barn red. YOu could go to a lot of different places at different times for ingredients you didn’t have; in Alexandria, VA, the apothecary’s shop was popular. It is still there as an exhibit; the Washingtons (Geo. & Martha) shopped there. Robert E. Lee was there when he recieved word of John Brown’s attack on the arsenal at Harper’s Ferry; a plaque marks the spot. The EPA went nuts when the place was reopened as a hsitoric site, as there were “hazardous materials” in the waste disposed of through the years in the basement.