Exposing older cars to winter’s unfavorable elements—specifically, the dual-pronged attack of moisture and road salt—is a quick way to end up facing off with metal’s age-old nemesis: rust. Any classic car fan calling the Northeastern or Midwestern half of the country home has felt more than a passing twinge of envy for their compatriots in many southern and western states, who enjoy a drier climate that allows for year-round enjoyment of their rides without living in constant fear of the tin worm.
Corrosion, however, tends to attack vehicles of a certain vintage far more aggressively than their modern counterparts. It’s not just a question of being “old,” either. In certain eras, brand-new cars could shed their metallic skins while still sitting in the showroom.
The answer as to why today’s vehicles are more resistant to such a sudden fate is somewhat complex. Automotive industry’s long, slow march toward more durable materials is the result of advancements in design, engineering, and manufacturing, as well as the corporate buy-in required to implement an actual anti-corrosion plan.
Zinc it up
A key defense shield used by every automobile currently sold in the United States: galvanization. This process coats steel with a layer of zinc, most typically by “hot dipping” components in a molten vat of the metal (although painted components see a thinner layer deposited via electroplating). Some steel even comes to factories pre-galvanized, which means only parts that are sliced, abraded, or otherwise cut and exposed require a re-application of zinc to retain their rust-proof profile.
The effectiveness of galvanization relates to the chemical properties of the corrosion process. Rust requires a metal willing to give up its electrons (called an anode) to another piece of metal that is willing to receive electrons (a cathode). Facilitating this transfer is something called an electrolyte, typically a liquid that transports the electrons from A to B.
With steel, water serves as an effective electrolyte, particularly if it is mixed with calcium chloride (road salt) or even carbon dioxide from the atmosphere, which creates liquid carbonic acid. Steel is all too happy to be its own anode and cathode, allowing the metal to have its electrolytes stripped when wet. This effectively dissolves the iron and encourages it to bond with the oxygen that breaks free from water during the entire transaction. The end result: iron oxide, or rust.
How does galvanization fit in? Zinc is even more free-spirited with its electrons, and layering it on top of steel sees it sacrificing them to the clutches of corrosion. In effect, zinc takes one for the team, over an extended period of time, to keep steel spotless and strong.
Who needs progress?
All of the above sounds like a truly modern miracle in the fight against automotive entropy. The truth is more complicated. Galvanization has been around for more than 250 years, seeing innumerable industrial applications during that time. The Brooklyn Bridge used almost 15,000 miles of galvanized wire when it opened in 1883, and galvanized trash cans have been littering the curb since the early 1900s. Car companies, however, would wait nearly another hundred years before taking advantage of zinc’s protective properties on anything approaching a wide scale.
Why did the automotive industry lay off galvanization for so long? There’s more than one answer, but it starts with the fact that up until the 1950s, the steel used to build passenger cars and light trucks was much thicker—up to three times as much—than what is currently used. Thus, thicker still was its own crude version of rust protection, as it took considerably longer for major components such as the frame or suspension to rust all the way through.
The cult of consumerism would achieve its apex in the 1950s and convince drivers that a new car every couple of years was a completely reasonable expenditure to make. This cycle was reinforced by brand-new body styles every 12 months combined with the desire to put the drab, rationed existence of a still-fresh world war in the rearview mirror.
Reach, meet grasp
To recap: yes, early cars were still susceptible to rust, but they were thickly built to the point that most had been sent on their way in favor of something new before their original owners started to notice any major problems.
That all started to change in the early 1970s. Automakers were slowly switching over to unibody-type construction as well as more ornate and elaborate vehicle designs in almost every segment of the market. At the same time, the Big Three felt increasing pressure to produce lighter, more fuel-efficient automobiles while also cutting costs, which meant moving towards increasingly thinner gauges of steel.
It was a recipe for disaster that would produce nearly 15 years of rust-vulnerable automobiles, vehicles with expiration dates looming a mere two or three years after they had been built due to their extreme susceptibility to corrosion in oxidation-friendly regions. Sound dramatic? Not if you lived through it. In fact, Chrysler’s own data from the era suggested that one in five winter climate cars featured rust holes after a mere two years on the road, which jumped to more than half after another two years.
All those folds and seams in vehicle designs Detroit was building were perfect for collecting moisture, dirt, grime, and salt, which in combination with the reduced steel content across the board dramatically accelerated the corrosion process. Plastic and rubberized undercoatings meant to deaden sound or even protect against salt spray actually ended up further nestling water and calcium chloride against vulnerable components.
Laissez-fair attitudes towards quality control certainly didn’t help, either. Sub-par vehicles not infrequently showed up on dealer lots, often with trim or paint missing, which left metal exposed to the elements and ripe for a visit from the rust fairy. It was not uncommon for brand-new vehicles to require some type of rust repair right out of the box.
The American car-buying public was fairly tolerant of this entire state of affairs—right up until imports started arriving to demonstrate that there was an alternative to Flintstone-ing your feet through the floorboards after several winters.
Some low-production European car companies such as Rolls-Royce (with the 1965 Silver Shadow) and Porsche (the 1976 911) had already begun to embrace galvanization, but it was the sheer number of cars pouring out of soon-to-be-powerhouse Japan that would turn the tide.
Japan had long sought better anti-corrosion technologies, as the island nation was under constant attack from salty sea air that quickly ate through the thin, lower-quality steel that its nascent automakers were initially forced to use. It was even worse once these products made it into the Thunderdome of America’s winter-ravaged roads. Intent on developing a stronger domestic steel industry, Japan approached galvanization with gusto. By the mid-’80s Japanese cars had lost their reputation for Swiss cheesing and instead began to put the pressure on Detroit to follow suit—in more ways than one.
Not only did Ford, Chrysler, and General Motors begin to implement stronger anti-corrosion treatments to the metals used in constructing their respective vehicles, but they also began to simplify their designs. This move was done in part to reduce or eliminate the many nooks and crannies that signed a moist, salty winter death warrant for so many automobiles, imitating the cleaner production methods of the Japanese. Although it didn’t inspire an immediate revolution, the C4-generation Corvette for 1983 sought to rectify the steel corrosion issues of its predecessor by using lots of galvanized steel as well as aluminum components. Even Stuttgart would take lessons from Hiroshima and Yokohama, introducing plastic fender liners on the 964-generation 911 (1989–94) to help eliminate the complaints of Carrera and SC owners fed up with wheel well corrosion.
No easy answers
It took almost a century for the auto industry to move from a total disinterest in the prospect of rust protection to a dedicated effort to make good on the multi-year perforation warranties that became commonplace by the time the ’90s rolled around.
Sandwiched right in the middle is the collector car danger zone of distinctive (albeit complex) body designs, moist undercoatings, and bare, thin steel that did not adequately protect many vehicles. If your passions happen to intersect with the cars of this era, you’re likely familiar with how effectively mother nature thinned the herd over time.
Aftermarket anti-rust treatments and protectants are out there, and while they offer varying degrees of protection, none of them can be said to 100 percent account for the accelerated decay of vintage metal. Unless you’re willing to strip your vehicle to the bone and invest in your own hot dip setup (not as delicious as it sounds, at least financially), the safest thing you can do to protect your classic from a crunchy fate is to keep it away from salt and park it in a dry, well-ventilated area once the snow flies. After all, that’s why the automotive universe invented the winter beater.