Hello and greetings to all readers!
I've been following this forum for a while, and I learned quite a lot from it.
What I noticed as the best "feature" of this forum is that most of the opinions given are are proper, professional or extensive experience-based opinions.
Most other forums which deal with any kind of metallurgy-associated topics contain a lot of "information noise" - many wrong information or hastily concluded opinions.
That is why I would highly appreciate help in definitely determining how to achieve the most durable and longest lasting underbody protection for a road vehicle.
I have already searched for and read a lot of similar topic on this forum.
-------------
Introduction
-------------
I have talked with numerous car body repairers about this topic, and read thousands of various Internet forum topics, web page articles, etc.
The only definite conclusion which I made at the end is that there are dozens of wrong methods and possibly only or two proper ones.
I also concluded that many people do "what a paint shop salesman recommends", "what others usually do" or "what my ancestor used to do", so there are many falsely acquired methodologies circulating around.
During my investigations, I also read various dedicated old timer forums, off road enthusiasts forums, car detailer forums, etc.
To point out again - the aim is to have the most durable and longest-lasting underbody rust protection. Durable means preferably at least 10 years, or much more.
Let's assume that a vehicle will be used in the worst operating conditions - plenty of salty roads, high-speed gravel driving, off road driving through deep mud and over rocks.
Therefore, the underbody will be coated in salt, will sustain lots of small rock chipping, will have thick mud deposits on it, and it will occassionally encounter strong hits from big stationary rocks.
The underbody will ocassionally be power washed. Such water jets can be quite strong and abrasive.
If a certain underbody coating system can endure all this in the long term (except possibly strong hits from big rocks of course), then it can certainly endure much more "normal" operating conditions.
The main risks for underbody coating failure are:
- wear-off;
- chip-off;
- cracking;
- delamination;
Wear-off can for example occur due to pressure washing (then called "wash-off ). This causes immediate need for re-application.
Chip-off usually happens due to mechanical impact. I should be easy to notice and remedy in due time.
Cracking is still usually possible to notice (depending on the type of coating), and can be remedied in due time.
However, delamination tends to stay undetectable and traps water behind, leading to catastrophic rust development behind.
-------------------------
Materials and procedure
-------------------------
Let's also assume that the coating application begins from bare metal.
I have completed some pieces of the main puzzle, but I am stil missing two main pieces.
Regarding the application process and material selection, this is what I have determined so far:
1.
Mechanically clean all existing rust and old coatings (wire brushes, sand blasting, etc.).
2.
De-grease the bare metal surface (white spirit, engine degreaser, or something else?) and wipe off.
3.
Apply a rust converter chemical on areas where tiny bits of rust still remain, or on areas where old rust was removed with wire brushes (as they rarely remove 100%).
Then wait for it to convert.
4.
Spray two coats of primer coating.
It appears that epoxy primers are the best as they stick very well, everything else sticks to them very well, and they are waterproof, even for long term.
5.
Smear seam sealant over the epoxy primer wherever there is an existing weld or any other fixed metal sheet joint.
It appears that polyurethane sealers are the best, but I don't know why.
6.
Optional: Spray an additional coat of epoxy primer over the sealant (but after the sealant has fully cured).
7.
Spray a stone chip resistant coat, preferably in two layers.
Possible coating types: bitumen-based, synthetic rubber and resin based, epoxy based, polyurethane based, wax, anything else?
8.
Optional: Spray automotive wax over the stone chip coat (if the coat in step 7 wasn't wax already).
Reason: It provides an additional repulsive layer and it also has a bit of "self-healing" property after being stone chipped.
9.
Take a good holiday.
Now, I would like to hear second opinions if I have missed anything in this procedure, or if something should be done differently or with different kind of materials.
I will write the second part of this in my next response, as the web site does not allow overly large posts to be made.
I've been following this forum for a while, and I learned quite a lot from it.
What I noticed as the best "feature" of this forum is that most of the opinions given are are proper, professional or extensive experience-based opinions.
Most other forums which deal with any kind of metallurgy-associated topics contain a lot of "information noise" - many wrong information or hastily concluded opinions.
That is why I would highly appreciate help in definitely determining how to achieve the most durable and longest lasting underbody protection for a road vehicle.
I have already searched for and read a lot of similar topic on this forum.
-------------
Introduction
-------------
I have talked with numerous car body repairers about this topic, and read thousands of various Internet forum topics, web page articles, etc.
The only definite conclusion which I made at the end is that there are dozens of wrong methods and possibly only or two proper ones.
I also concluded that many people do "what a paint shop salesman recommends", "what others usually do" or "what my ancestor used to do", so there are many falsely acquired methodologies circulating around.
During my investigations, I also read various dedicated old timer forums, off road enthusiasts forums, car detailer forums, etc.
To point out again - the aim is to have the most durable and longest-lasting underbody rust protection. Durable means preferably at least 10 years, or much more.
Let's assume that a vehicle will be used in the worst operating conditions - plenty of salty roads, high-speed gravel driving, off road driving through deep mud and over rocks.
Therefore, the underbody will be coated in salt, will sustain lots of small rock chipping, will have thick mud deposits on it, and it will occassionally encounter strong hits from big stationary rocks.
The underbody will ocassionally be power washed. Such water jets can be quite strong and abrasive.
If a certain underbody coating system can endure all this in the long term (except possibly strong hits from big rocks of course), then it can certainly endure much more "normal" operating conditions.
The main risks for underbody coating failure are:
- wear-off;
- chip-off;
- cracking;
- delamination;
Wear-off can for example occur due to pressure washing (then called "wash-off ). This causes immediate need for re-application.
Chip-off usually happens due to mechanical impact. I should be easy to notice and remedy in due time.
Cracking is still usually possible to notice (depending on the type of coating), and can be remedied in due time.
However, delamination tends to stay undetectable and traps water behind, leading to catastrophic rust development behind.
-------------------------
Materials and procedure
-------------------------
Let's also assume that the coating application begins from bare metal.
I have completed some pieces of the main puzzle, but I am stil missing two main pieces.
Regarding the application process and material selection, this is what I have determined so far:
1.
Mechanically clean all existing rust and old coatings (wire brushes, sand blasting, etc.).
2.
De-grease the bare metal surface (white spirit, engine degreaser, or something else?) and wipe off.
3.
Apply a rust converter chemical on areas where tiny bits of rust still remain, or on areas where old rust was removed with wire brushes (as they rarely remove 100%).
Then wait for it to convert.
4.
Spray two coats of primer coating.
It appears that epoxy primers are the best as they stick very well, everything else sticks to them very well, and they are waterproof, even for long term.
5.
Smear seam sealant over the epoxy primer wherever there is an existing weld or any other fixed metal sheet joint.
It appears that polyurethane sealers are the best, but I don't know why.
6.
Optional: Spray an additional coat of epoxy primer over the sealant (but after the sealant has fully cured).
7.
Spray a stone chip resistant coat, preferably in two layers.
Possible coating types: bitumen-based, synthetic rubber and resin based, epoxy based, polyurethane based, wax, anything else?
8.
Optional: Spray automotive wax over the stone chip coat (if the coat in step 7 wasn't wax already).
Reason: It provides an additional repulsive layer and it also has a bit of "self-healing" property after being stone chipped.
9.
Take a good holiday.
Now, I would like to hear second opinions if I have missed anything in this procedure, or if something should be done differently or with different kind of materials.
I will write the second part of this in my next response, as the web site does not allow overly large posts to be made.