[69 widetrack]

Originally Posted by wayne gillis

I agree with stripping it down to bare metal with 80 grit , than applying some
etching primer to protect against rust .

Etch Primer will work and is an excellent product, however, with the epoxy technology being what it is today it is basically a glue (epoxy) with rust inhibitors in it, they have much more build than an etch and some, depending on brand, have respectable sanding qualities. This allows the individual to either go from metal, to Primer to top coat (wet on wet), or from metal to primer to block sand to top coat. It's all a personal preference, both work well.

Yesterday, I stripped a frame, 2 coats epoxy, flash, 2 coats satin black poly urethane. Worked very well. Etch primer, without the build properties, would require another top coat to fill the profile of the metal after stripping, where as the epoxy did fill the profile, gave the rust protection and allowed me the wet on wet process in order to complete the task in one day.

The frame I did is not for a vehicle that is going to be exclusively shown at car shows, it's a show driver, rain or shine. On the other hand, if it was a show car only (Trailer Queen), when basically time and budget constraints where not an issue, I would prefer the method of either the etch or epoxy, 2K high build, block sand and top coat, not only for the frame but, the entire car.

Hope I explained it well enough.

Ray

[novafreek6872]

Ray,

seems like the good epoxy primers out there today have pretty much replaced any need for etch primer, no?

Maybe use etch on smooth metal that has not been sanded?

Trying to figure it out

[69 widetrack]

Originally Posted by novafreek6872

Ray,

seems like the good epoxy primers out there today have pretty much replaced any need for etch primer, no?

Maybe use etch on smooth metal that has not been sanded?

Trying to figure it out

First off there are 2 types of adhesion, mechanical and chemical, to get the best results both should be recommended. I would rough up any metal, for insurance purposes to achieve a better mechanical adhesion...You've got it there, it's not going to take that long to rough up the metal slightly to ensure a better adhesion, why not do it? If your using etch, I wouldn't top coat directly over etch on a large surface regardless. It's a product that's applied thin and with the expansion and contraction differences in metal versus top coats, a buffer zone of primer like epoxy or 2K, I feel gives longer lasting results. Etch I feel is excellent for small burn through's on edges etc. (I mean small burn through's) and then top coat. So etch still has it's purposes and still sold with good results.

This is a debate...it's the same old story, I did a seminar on this about a year ago and one of the people asked me what I preferred, I told him that I liked epoxy and explained why (as I did in my previous response), another guy stood up and said he did a test, one panel with epoxy (PPG DPLF 40) and one with Nason etch primer, left both panels out in the elements for 1 year and the etch stood up much better than the epoxy, apparently the epoxy lifted around the edges and started to rust.

I asked him how the metal was prepped and where they both prepped the same, he started getting upset and told me of course they where and that it was a stupid question. I asked if he allowed the proper induction time for the epoxy (not required for all epoxy primers but for DPLF 40 you need to mix your primer and let it sit for awhile before apply it)...he asked what induction time was....did this cause the epoxy to fail in comparison to etch, I don't know, I wasn't there to see what happened but if he didn't know what induction time meant, chances are he didn't follow instructions and when they aren't followed your guess is as good as mine.

I've used both, believe in both, but, prefer epoxy for the reasons I mentioned earlier, is one better than the other as far as preventing rust. I'd say rust prevention or minimization is more about prep more than product, they both work if you follow instructions, if you get rust after applying a rust preventative product correctly, chances are you screwed up somewhere else.

I would say over 90% of warranty claims I paid out where not product failure, they where more to keep a good customer that had human failure happen. This is not to say that products don't fail, I remember a clear coat from a major manufacturer in the early 90's that consistently yellowed, that was product failure and was recalled and warranty was paid, but that is more uncommon than common.

Hope this explains the differences between the 2 products.

Ray

[MARTINSR]

I have to tell you, you can warp the hoods or roofs on those cars EASY with a sander. You have to be very careful to use NEW. SHARP, QUALITY paper and change it often and not work in one area long.

But I have to tell you, at the shop, that sucker gets chemically stripped we never strip large panels like a hood, trunk or roof with a sander.

If the whole part needs to be stripped (they usually do) then that part comes off the car usually, if it is a bolt on. A hood, no brainer, it gets pulled off and set on a stand and stripped with Aircraft stripper. The roof, the car gets bagged with plastic masked off at the roof protecting the sides of the car and it gets stripped with Aircraft stripper.

You have to give it a lot of respect, but that striper saves a lot of time.

Brian

[MARTINSR]

Originally Posted by 69 widetrack

First off there are 2 types of adhesion, mechanical and chemical, to get the best results both should be recommended. I would rough up any metal, for insurance purposes to achieve a better mechanical adhesion...You've got it there, it's not going to take that long to rough up the metal slightly to ensure a better adhesion, why not do it? If your using etch, I wouldn't top coat directly over etch on a large surface regardless. It's a product that's applied thin and with the expansion and contraction differences in metal versus top coats, a buffer zone of primer like epoxy or 2K, I feel gives longer lasting results. Etch I feel is excellent for small burn through's on edges etc. (I mean small burn through's) and then top coat. So etch still has it's purposes and still sold with good results.

This is a debate...it's the same old story, I did a seminar on this about a year ago and one of the people asked me what I preferred, I told him that I liked epoxy and explained why (as I did in my previous response), another guy stood up and said he did a test, one panel with epoxy (PPG DPLF 40) and one with Nason etch primer, left both panels out in the elements for 1 year and the etch stood up much better than the epoxy, apparently the epoxy lifted around the edges and started to rust.

I asked him how the metal was prepped and where they both prepped the same, he started getting upset and told me of course they where and that it was a stupid question. I asked if he allowed the proper induction time for the epoxy (not required for all epoxy primers but for DPLF 40 you need to mix your primer and let it sit for awhile before apply it)...he asked what induction time was....did this cause the epoxy to fail in comparison to etch, I don't know, I wasn't there to see what happened but if he didn't know what induction time meant, chances are he didn't follow instructions and when they aren't followed your guess is as good as mine.

I've used both, believe in both, but, prefer epoxy for the reasons I mentioned earlier, is one better than the other as far as preventing rust. I'd say rust prevention or minimization is more about prep more than product, they both work if you follow instructions, if you get rust after applying a rust preventative product correctly, chances are you screwed up somewhere else.

I would say over 90% of warranty claims I paid out where not product failure, they where more to keep a good customer that had human failure happen. This is not to say that products don't fail, I remember a clear coat from a major manufacturer in the early 90's that consistently yellowed, that was product failure and was recalled and warranty was paid, but that is more uncommon than common.

Hope this explains the differences between the 2 products.

Ray

Very good explanation of the two products. Not science type explanation but simply the "whys" in plain english.

Brian

[mr4speed]

Brian, good call on the stripping of hoods, and roofs, and I will also add trunk lids as well. I don't know about any one else out there but I have had a tough time stripping the inside of hoods and trunk lids even using a wire wheel. The heat from this is enough to completely destroy a nice straight panel. The other way to destroy for sure is sandblasting the insides of these panels. It is very hard to believe that the little bit of heat from these stripping techniques will damage anything, but just beware it will for sure.

[69 widetrack]

Thanks Brian, I very much appreciate your comments. Chemical stripping is a very viable and safer (especially for the panel) method of stripping large panels, it minimizes the chance of warping. It should also be noted that you mentioned to use New, Sharp and Quality when using sand paper to strip a large panel or any part for that matter...I would agree with this comment 100%...VERY IMPORTANT...As your using the abrasive, it start to loose it's (grit) cutting power and creates heat, the coarser the grit and speed of the machine, the more heat. Think of it this way, when grinding a weld smooth with a 36 or even 50 grit disc, it's easy to see the heat marks, the metal can turn blue from heat very quickly. If the machine is used in only a small area, it also creates excessive heat in that area causing the panel to warp. The combination of these factors coupled with thinner metal on newer cars and perhaps inexperience on the part of the person performing the task, can lead to an expensive and time consuming situation. This is critical enough to say that even experienced persons can experience this problem. when using abrasives versus chemical means to strip a large panel.

Good call on deck lids Mr4speed, I had a very experienced individual stripping an aluminum deck lid on a Mercedes a while back and it cost me a lot of time and money...He would get a reaction to the chemicals in Aircraft Stripper and refused to use it, but, didn't want to tell me about his reaction to stripper, started to strip the trunk lid with paper and it warped, so I paid the tab.

This is not to say that using abrasives won't work, they do, but whenever possible, conditions allowing (the odor seems to be more nasty for some than others...like my wife) chemical stripper is a safer route for the larger panels, especially larger panels that don't have body lines in them.

[69 widetrack]

Originally Posted by mr4speed

Brian, good call on the stripping of hoods, and roofs, and I will also add trunk lids as well. I don't know about any one else out there but I have had a tough time stripping the inside of hoods and trunk lids even using a wire wheel. The heat from this is enough to completely destroy a nice straight panel. The other way to destroy for sure is sandblasting the insides of these panels. It is very hard to believe that the little bit of heat from these stripping techniques will damage anything, but just beware it will for sure.

This is so true, let alone the heat problem that go along with trying to get into the little recesses and underneath braces...the cuts to your hands, or ripping up a perfectly good sanding pad when you catch an edge.

Thanks for posting this information Mr.4 speed

[wayne gillis]

Thanks for the explanation 69 widetrack , I was just given him a starting point .

[69 widetrack]

I'm glad you brought it up Wayne, it's a question that comes up often, even in the professional arena and could help others understand the differences in usage.