How to avoid corrosion in automotive evaporators

I live in Caracas, Venezuela, a large city oversaturated of vehicles. I and a lot of other auto owners have been experiencing the need to replace the a/c evaporator after 2 or 3 years of use due to failure caused by corrosion. I personally have done it two times in the last 4 years in two different cars.

Considering the facts that I could be living in heavy sulfur dioxide environment because of the heavy traffic (60% or more of the vehicles still use leaded gas), plus other manufacturing restrictions that make the evaporators weaker, I would like to know if there are any type of elastomer coatings I could use in a automotive aluminum evaporator to avoid corrosion and have last at least 5 or 6 years?

Are there any type of elastomers coatings or any other type of proposal that can be used to protect automotive evaporators against corrosion?

I am about to replace the evaporator on my A4 Audi and because of the extent of the job I have contemplated this same question. I work in the aviation industry and we use a chemical treatment on all aluminium alloy whether its going to be painted or not. It's a chromate finish that penetrates the surface of the material and leaves a goldish appearance if done properly. The surface must first be etched with a product called Alumiprep 33 ⇦ on eBay or Amazon [affil link] then rinsed with water and dried. Then Alodine 1201 ⇦ on eBay or Amazon [affil link] is applied on the surface preferably in a bath for a few minutes until the color of the surface changes. The part must then be removed and rinsed under running water, then dried.
I was able to get these two chemicals at a boating shop.
The instructions for use is on the containers. Please share your thoughts on this. Cheers. Hyat