Our mechanic said he noticed a lot of rust on the underside of our 2014 CX-5 Touring AWD. The body and car are in great shape, but I really want to keep the car a LONG time and would like to get something done to help control the under-body rust. Do any of you have suggestions?

 

I'm a little out of date on this but many shops used to put the vehicle up on a lift and apply spray undercoating, esp in the fender wells. Seems like the mechanic would have suggestions.

 

The problem with the undercoating they used to do is that it captures moisture and actually accelerates rust.

 

rinsing the underside of your car periodically will help keep the rust at bay.

 

I do not know where you are writing from but here in the Nordic countries they use salt on the road during winter and that creates a lot of rust problem for cars. It is quite common here that cars under go a sort of rust proofing with anti rust wax coating at the factory (Volvo etc) or on the port of arrival e.g. Mazda etc. There is a very comprehensive rust control test done by a car magazine that tells you how well the rust proofing has been done on new cars sold in Sweden. If it has been done unsatisfactorily and you plan to keep the car for a long time, then proper rust proofing is advisable. They inject antirust wax inside the hollow beams and spaces of the car body and spray paint the under side with thicker anti rust wax. I am sure it is available in your country too. Just to give you an idea on the rust proofing in Mazda CX-5 sold in Sweden, here is the google translation from " vi bilagare" car magazine from 2015. CX-5 got 4 out of 5 points for rust proofing.

All parts of the body are made of steel sheet. The bonnet has uneven interior treatment and poor corners. Under the front wheel arch there are sound absorbing cushions that absorb moisture. The tailgate is rustproof in the bottom but has no seal in the corners. The doors have good joints and are sealed inside, but the plastic strips in the bottom edge collect dirt. There is moisture insulation between the windscreen pole and the door. Tank of sheet metal, inner lining of felt material, plastic front. The backing is covered with plastic sheets, the joints are well sealed. A lot of rustproofing in all beams, Mazda does an anti rust treatment on cars for the Swedish market in Holland. Rot/rust protection guarantee: 12 years.

 

My current mechanic charges me to spray the underside of a vehicle with used motor oil. He aerosols the oil in has compressor and sprays, does it twice a year. His farm truck has over 350K on it and little to no rust. There is a product that is the wax like product that you can spray under a car, comes via a can. The rubberized undercoating sprays trap moisture and accelerate rust. Krown is a service that does the waxy undercoating sprays, Drill some small holes in the impossible to reach areas and then puts a rubber grommet in the hole when finished. I thought i saw a price of around $150 to do a car.

 

here is a development on rust proofing in mazda cx5. I had my new cx5 checked by the rust proof guy and he found rust proof wax only in the horizontal hollow beams going from front to back (where you rest your jack stands on either sides, left and right). Is Mazda half telling the truth when they say that they have rust proofed it at the harbour at Holland or Belgium. The suspension arms and steering links both front and rear were completely bare of any antitrust treatment. I chickened out and had it rust proofed with the environmental friendly linseed oil. Cost only 260 Euro. Next application after two years.