Hey any chemists on here?

[Dutch]

I went to clean the accumulated water spots off my motor and my hydrochloric acid bottle sprayer was broken so I looked around my cleaning supplies and found lemon scent all purpose cleaner.  I thought what the heck and sprayed it on the motor, let it set a couple of minutes, hit it with a shop brush, then rinsed it off.  Much to my surprise the water spots along with the dirt is gone.  I looked at the ingredients and found:

oclyl decyl dimethyl ammonium chloride

dioclyl dimethyl ammonium chlorinide

didecyl dimethyl ammonium chloride 

alkyl dimethyl benzyl ammonium chloride 

What do I have here?

[Terrierman]

Sounds like lemon scent all purpose cleaner to me.

[Dutch]

That’s what it says.  The way it did the hard water spots has me wondering about the motor finish.

[fishinwrench]

The painted finish on outboards is a 5-step process.   

Prep-sol

Aluminum oxide primer

Paint

Clear coat 

Wax

The wax and clear coat goes away really fast, it's no match for heat and sun exposure.  Water spots (calcium deposits) that don't wipe away easily are adhering to the paint....the clear coat is already gone.  So anything that removes them is also taking a bit of paint too. 

[top_dollar]

22 hours ago, Dutch said:

I went to clean the accumulated water spots off my motor and my hydrochloric acid bottle sprayer was broken so I looked around my cleaning supplies and found lemon scent all purpose cleaner.  I thought what the heck and sprayed it on the motor, let it set a couple of minutes, hit it with a shop brush, then rinsed it off.  Much to my surprise the water spots along with the dirt is gone.  I looked at the ingredients and found:

oclyl decyl dimethyl ammonium chloride

dioclyl dimethyl ammonium chlorinide

didecyl dimethyl ammonium chloride 

alkyl dimethyl benzyl ammonium chloride 

What do I have here?

               They are all common household detergents.  Soaps and detergents all work by the same basic fact that you can easily dissolve salt in water, but cannot dissolve oil in water.  The molecules you listed are large, generally linear, molecules that are very greasy (non-polar) on one end, and very salty (polar) on the other.  Most debris that needs to be cleaned is made of organic material that is largely non-polar.  Water is a very polar molecule and a polar solvent will not dissolve a non polar solute very well.  Since detergent has both a polar and a non polar end, it forms what is called a micelle around organic particles where the greasy end surrounds the particle, and the salty end can be dissolved in water.  So when you add soap to dirt and let it set for a few minutes, it forms micelles around the dirt and it is easier to clean with water.  

       

 

[Dutch]

top_dollar thanks for the explanation.  I’m not sure I grasp it all but I do feel better informed.

[top_dollar]

14 minutes ago, Dutch said:

top_dollar thanks for the explanation.  I’m not sure I grasp it all but I do feel better informed.

Sure no problem.  It is pretty rare that someone has a question about chemistry, so I am always happy to chime in.  It tends to be a largely useless skillset except for very niche applications.   

[tjm]

@top_dollaris it true that by removing the water spots with detergent that paint is also being removed?

[top_dollar]

27 minutes ago, tjm said:

@top_dollaris it true that by removing the water spots with detergent that paint is also being removed?

               Not on an outboard motor or boat unless the cleaner has some abrasives or you're really scrubbing really hard.  I actually work as a chemist for a paint company.  Any paint that is on an outboard should be robust enough to not come off with detergents, and even most solvents/chemicals.  Long term exposure to acids/bases, high humidity, and sunlight are going to be the hardest thing on boat and car paint.  Everyone has seen the hood of an old car where the sun has turned the clear really chalky and white, that cannot be cleaned off as that paint is destroyed.

               If a painted part is left under very high humidity for long periods of time, water molecules will get trapped in the clear coat itself causing what look like water spots.  Those wont get cleaned off though as by that time the problem is in the paint.  If they are not too deep, you can sand/buff/polish it, but you need a thick layer of clear coat or apply fresh clear for that. 

[retired chem teacher]

glad to see another chemistry person here.  Taught high school chemistry and physics for 40+ years.   All of your info is right on.