A number of people have been asking about restoring rusted panels on vehicles lately so I thought I would go over some of the best methods to prepare a severely rusted hood for paint. The unfortunate thing about heavily rusted parts is that the rust its self is reducing the thickness of the remaining metal. This is worse when the rust is on both sides of the panel and at some point a rusted panel just is not worth saving. In this how to we will cover the differences of new and classic vehicles and what methods are best for restoration.
How do you determine if it is better to replace a part vs trying to save it?
This can be difficult at times but when the availability of the panel either by OEM or Aftermarket sources is very had to find then sometimes you really don’t have much choice.
A friend that restores classic cars almost exclusively in his business goes through this problem with almost every vehicle he works on. It has got to the point where the best way to restore one vehicle is often buying one or two parts vehicles. This is kind of sad to think three possibly restorable vehicles are giving their life for one but for some makes of vehicle you just can’t find new parts.
Cost can also be a factor. Patching panels instead of replacing full panels is common. Even if you can’t find an aftermarket patch panel you can often make up a part easier than finding a used one that doesn’t have the same rust damage that your vehicle has.
For newer vehicles you must be very careful when working with rusted panels that are made out of high strength steel. It is important to not attempt to patch these parts as the welding can weaken the structure. Entire parts must be replaced at the spot welds and manufacturer replacement procedures must be followed correctly. The use of Ultra High Strength Steel in New vehicles will mean that they can not survive. Eventually replacement parts will not be available and using any other method but the OEM’s to restore them will mean a weaker structure, frame, which could result in catastrophic injury if the car is in an accident. Basically every vehicle made after about 2015 will be a throw away vehicle after 10 years when the OEM no longer has to furnish parts.
Restoring Rusted Automotive Panels
There are a variety of ways to remove rust from panels. Many people will go with a sandblasting or media blasting option which makes removal pretty easy. The problem with media blasting is the surface is left very rough and it will still need to be prepared with a grinder before painting. This can be a big task but sometimes it is the best option when the interior and underside of the vehicle is fully rusted.
If you are preparing just one panel or do not have interior rust then it is possible to grind the surface with a flap disk or grinding disk that is between 30 and 60 grit to remove most of the rust. At that point as you see in our photo you will have remaining pitting. You do not want to remove all of the rust in these pits with a grinder or you will be eating away good metal that is important for the structure of the panel.
Whether you removed most of the rust through blasting or grinding it is now important to use a rust converter. If your panel is lap welded, overlapped and spot welded, it is important to treat the seams and any other remaining rust with a rust converter that will turn the iron oxide into a stable substance called magnetite. At that point you can then paint the panel with primer and seal the seams.
Unfortunately the rust converter will leave the panel in a rough condition so it is best to resand the surface with a higher grit paper. This will remove some of the converted oxide and may reveal remaining rust. If you find rust you must retreat it. This often occurs when the initial removal of rust was not completed fully. Some people even suggest not sanding initially but this will most definitely cause rust to remain under the converted surface and this will cause rust to return to the panel in a short time.
Final Note
As you can see there are times when you have no other choice but to try to restore a rusted panel. Often that is due to availability. However if the part is so far gone there is no way to remove the rust and continue using the panel. You will either have to patch in new metal or find a panel in better or new condition.
Additionally we went over the use of high strength and ultra high strength parts in new vehicles. If you find rust on these panels they must be replaced entirely. Do not try to make repairs to these parts. Grinding or blasting will remove too much metal and patching by welding is not allowed.
When selecting a vehicle for restoration you really need to do your homework on what parts are available and that means new OEM, Aftermarket and Used Parts.
Often if you are dealing with a relatively recent make vehicle you can find a used hood, door or fender in the same color as your vehicle and if the color match is not bad then you won’t have to pay for paint.