Products and how they affect water behavior


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This is a really sciency question that needs a chemist to answer. Unfortunately, I don't personally know any but who better to ask than Dr. G himself (albeit indirectly through this forum).  I'll ask what I think is the right question first and then explain what I've done that's got me thinking about this.

Question: What attributes of a chemical's make up play a role in how water behaves on a surface it's been applied to, even after it's been rinsed? And how specifically do those attributes affect it? In this particular case, I'm asking about how various non-LSP chemicals react on a coated surface (Gloss Coat for instance). I would love an answer as detailed as Dr. G can give here. Perhaps not PhD level, but certainly college level.

Background: Today I was playing around with a panel that has 2 different SiC based coatings on it trying to decontaminate it but also maybe seeing what I could do to kill it. The coatings are around 7-8 months old at this point and not performing like they did when new so I decided to try to chemically and mechanically decontaminate it to see what would happen.

After an ONR wash, the water behavior was really poor. Water would pool and then sheet but very, very slowly. My first step was to spray Ferrex and clay with the OPT/TRC clay towel. After a thorough agitation and rinse, I noticed an improvement in water behavior, probably due to the removal of surface contaminants no doubt. But after my next experiences, I'm wondering if the chemical itself played a role.

My next step was to try an acid to remove water spots from hitting the panel with hard water so I sprayed Meg's Wheel Brightener diluted 1:1 and agitated with a clean microfiber before rinsing. After a thorough rinse the water behavior on the panel improved even more, getting as close to "new" as it had been in a long while. No amount of additional rinsing seemed to make this water behavior any better or worse.

My final product would be an alkaline, as that is commonly suggested for coating decontamination. For this I sprayed Power Clean at full strength, then agitated and rinsed like I did with the wheel acid. This time, however, the water behavior didn't get better. It actually made the panel completely flat, as if no protection were on it at all. No amount of rinsing would improve the water behavior. I know that Power Clean can be used safely on GC as this has been pointed out many times before by folks at OPT so I know that I didn't strip the coating simply with one application of PC. My next thought was that there must be some component that isn't rinsing well that's affecting the water behavior. So I thoroughly sprayed the panel with Paint Prep and let it dwell for several minutes before agitating with a clean microfiber and rinsing. The water behavior didn't improve much if at all so I'm still wondering what's going on at this point.

I decided to go back to the acid to see what it does. But instead of spraying only wheel acid (and also spraying it on the whole panel) I decided I'd use two different acids on separate test spots to see what, if any, differences I noticed between the two.  I was still going to use the Wheel Brightener at 1:1 but I also used OPT MDR. Again I applied, agitated, and let dwell before finally rinsing. After the rinse I was a little surprised to see that some of the water behavior had returned and was most noticable on my test spots.

Having done all of that, I'm starting to wonder what role these various chemicals we use play in the water behavior we notice when spraying our cars down and why it happens even after thoroughly rinsing the product off. Is it something to do with the pH or is it an acid/base thing? Is it a specific component that somehow interacts with the coating leaving it more or less "susceptible" (for lack of a better word) to rejecting water? These are things I don't know but want to know. Any insight would be helpful.

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Dr G answered your very long and detailed post - hope you understand how rare it is to have the CEO of any company do that.

“Water behavior on a surface depends on how close the surface tension is to water. Water itself has a surface tension of 72 mN/m or dynes. The closer the surface tension is to 72 dynes the more sheeting you get and the further apart results in beading. For instance surface tension of waxes is around 35 dynes, silicones around 25 dynes, flouro polymers and ceramic coatings are around 15 dynes. Therefore ceramic coatings and fluoropolymers give you the best water repellency. 
 
The surface tension also depends greatly on what’s on the surface. If you have contaminants such as dirt, water spots/ mineral deposits, iron contaminants etc. will change the surface tension. This is why while using different cleaners you  continuously improved the water beading and surface tension up until you used Power Clean. I think after using Power Clean you need a lot more rinsing to remove all the residue before you get back to the surface tension of your coating. The cleaners themselves cause sheeting by bringing the surface tension of water and coating or wax together since they have a hydrophilic and a hydrophobic end since cleaners contain surfactants (surface active agents). I don’t think there was a need for Power Clean in this case and the other cleaners you used are more effective in removing contaminants. So this is all about surface chemistry and the surface tension. I hope this answers your question. “
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Ron, it is not lost on me that Dr. G is willing and able to answer questions like these. I especially did not expect a reply so soon as I know he is a busy man. His response definitely helped answer my question.

A definite lesson learned for me: use less Power Clean.

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Very interesting as to what products do what to a coating.  I've often wondered how one removes a surfactant blend like Power Clean after it does its job (aside from rinsing with large quantities of water).  Can ONR "bind" to surfactants to aid in their removal?

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truth be told, Dr G is always helpful but I'm not always willing to bother him (over protective?).  I always remind people to rinse Power Clean as it leaves a residue, and ONR is the recommended method because it offsets PC's pH.  I would think that ONR would encapsulate surfactants like it does pollutants.

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