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Acid Rain - Auto Paint Finishes Can Be Saved

By Ron Ketcham
from Automotive International

All of us have read seen TV shows, and heard horror stories about acid rain. Unfortunately most information regarding acid rain and automotive paint finishes is at least slightly incorrect or, in some cases, totally wrong. Let' s set the record straight and clear away all the old wives' tales about acid rain. With that accomplished, you should be able to explain to your customers what it' s all about.


Manufacturing plants, power-generating plants, internal combustion engines, jet engines, etc. all produce sulfuric dioxides, which are released in their exhaust fumes. Smog, well known in major cities, contains these chemicals. When smog settles on a surface such as an automobile fender it is known as industrial fallout, or IFO. When ozone, water and heat are applied to IFO it becomes acid rain, right on the paint' s surface.

You may ask, "Don' t catalytic converters on our cars get rid of sulfuric emissions?" Only partially . Whatever changes the converter accomplishes in the sulfuric compounds are reversed by the effect of ozone and water.

Nitric oxides are additional acid rain components. The nitrics were originally thought to be a large part of the problem. However, recent data have shown they are not a real contributor to acid rain problems on vehicle paint finishes . there are, of course, exceptions.

While all manufacturing plants contribute to the nationwide pollution problem, one type stands out as an example of a sever localized producer of acidic contaminates . paper or pulp mills. These mills use an acidic process to break down wood fiber. A major portion of the acid compounds utilized is nitric acid. The nitric acids combine with other acids emanating from the process to create a mini acid-rain belt in the area around the facility.

When the emitted acids combine with particulate matter and then settle on an automobile finish, severe acid etching may take place in a very short period of time.

As a result of this localized pollution problem, many paper mills have a car wash on site so employees can remove the acid compounds from their vehicles at the end of their work shift. Others contract with a quality local car wash to clean their employees' vehicles.

A far worse emission is hydrazine. This extremely active acid is a component of jet fuel. So a vehicle parked regularly around a major airport or in high-usage flight paths will be subjected to hydrazine acids on its painted surfaces. Hydrazine is extremely reactive to oxidizers such as ozone.

An oxidizer is any compound that spontaneously emits oxygen either at room temperature or under slight heating. Many chemical compounds react vigorously at ambient temperatures as the oxidizing process takes place. Hydrazine, due to its molecular chain of hydrogen and nitrogen atoms, reacts violently, eating at any surface where it is concentrated. Any of us who took basic chemistry in high school or college remembers our instructor' s caution: "Always add the acid to the water . never, never add the water to the acid!"

So what' s that have to do with acid getting on a car' s paint?

Here's what is so important to our understanding of acid rain and protecting the paint and reducing or eliminating its effect on the paint film.

  1. When acid rain lands on the paint film surface, it does no damage! That' s right; it does not hurt it one bit! However..
  2. The water evaporates from the paint film, leaving behind dry concentrates of the acid compounds, hydrazine etc. We now have a dioxide, or dry substance of the compound. The vehicle is subjected to water in the form of dew, rain, and the like. The acids are no longer dry. Water is made up of two hydrogen atoms and one oxygen atom. Oxygen is an oxidizer. Ozone is an allotropic form of oxygen, an oxidizer.
  3. The acid compounds start penetrating into the paint film and concentrating more and more each time the vehicle gets wet with plain water. Each time, these acid compounds eat away more of the paint' s resin system, the former and binder of the paint system. If you look at a highly- magnified cut-away of a base/clear-coat paint system, it resembles a sponge. The resin system is what holds the sponge together That is why acid rain damage is seen as an etch or pit. Part of the system has been corrosively eaten away.

Let's now put all of this into perspective:

  • Acids are generated by our industrial processes, whether in California, New Hampshire or Montreal.
  • These acids mainly cause paint damage when they concentrate and are re-exposed to water, ozone and heat.
  • Simply rinsing a vehicle with deionized water or tap water activates the acid concentrates.
  • The acid concentrates eat away the paint, creating discoloring, etches, and pits, which most consumers and even car care professionals think are water spots.


"El Niño" pumps warm, moist air into its area. If conditions are in sync with the jet stream, it pulls more warm, moist air out of the gulf right up through the center of the United States and Canada. Current projections by some weather observers are for 1997 to produce an El Ni&ntildeo pattern. Acid rain may very well be extremely active this year; resulting in hundreds of millions of dollars in paint damage.

As "El Niño" travels, it picks up industrial pollutants and generates acid rain. El Ni&ntildeo causes quick, short warm rains as well as heavy storms, The quick warm rains are more of a problem because:

  1. They deposit the acid-laden rain on vehicles that have warm or hot surfaces.
  2. Since the vehicles are warm or hot, the paint film is softer and more porous and allows the acids to penetrate into the film or lock onto it.
  3. The water quickly evaporates, leaving the acid in a concentrated form.
  4. It rains again and the process starts all over but in a more concentrated form.
  5. All the dark colored cars start showing "water spots" and then discolored spots as the acid rain progressively etches and pits. Eventually even the white and light colored cars start to show the same damage.
  6. Everybody gets mad at the automobile manufacturers and paint suppliers because they think the damage results from poor paint.
  7. Everybody is wrong -- there is nothing wrong with the paint -- they just don't know what's happening.
  8. You do-now! But what do you do about it?
  9. Saving the paint from the dreaded acid rain is really very simple, and everyone can do it.
  10. Automobile manufacturers use transit coating or a white plastic sheet to protect the vehicle during transportation against the damaging effects of environmental pollutants. But what can we do once the protective covering is removed? Read on, there is an answer.


  1. Have the paint "decontaminated" with an approved chemical system. It is a simple washing process, performed by trained certified professionals. It does absolutely no good to buff, polish, wax or paint-seal a vehicle that has been exposed to acid rain. Remember, the paint is like a sponge. The acids enter the sponge and are concentrated. Every time the vehicle gets wet, some moisture penetrates the sponge and reactivates them. The acids must be removed or, like that pink rabbit banging away at his drum, they'll just keep going and going, eating away at the paint.
  2. Once the paint has been decontaminated, have a high quality polymer paint sealant properly and professionally applied. Quality products contain polymers, co-polymers and amino functional resins. These components are heat and detergent resistant, and anti-corrosive. In other words, they fight off the effects of corrosives such as acid rain, the acid in bird droppings and industrial pollutants found in IFO.
  3. Have your vehicle washed at least once a week. Regular washing is perhaps the most effective deterrent (when combined with a quality polymer paint sealant) against acid rain.
  4. Remember: A little more time and a few more cents spent on regular maintenance of you vehicle could save you thousands of dollars later.