I'd like to paint my rear axle tomorrow. I'm using PPG chassis black paint over an epoxy primer. Both products are "shoot straight out of the can" type products but they can be thinned if necessary. I prefer to shoot them straight out of the can because I'm unsure about thinning.

My largest concern is that the humidity will be 65-75% with the temps in the 80-85 range. The temp is good for good paint flow, but I don't know if the humidity will be a problem, if that means I should or shouldn't thin the paint. I sure don't want to do this twice!

The axle is wire brushed to bare metal. I plan to wipe it completely clean with lacquer thinner prior to painting to make sure any traces of oil and grease have been removed.

And yes, I do have a resperator mask to wear while I paint! I do have a pretty decent syphon feed gun and a good compressor. I've painted chassis parts before with great results but I never paid much attention to the weather. I guess I'm getting more analytical in my old age.

You should be fine with the humidity, fact thats pretty low considering its almost always in the 80-90% here in Louisiana. However follow the manufactures tech sheet, if it specifies a reduction i'd stick with that. Do not attempt to spray while its foggy out, causes cloudiness.
Wiping it down with lacquer thinner is a bad habit to get into, proper procedure is to use a fast dry prep-sol and clean lint free rags.

Originally posted by JimD:

Wiping it down with lacquer thinner is a bad habit to get into, proper procedure is to use a fast dry prep-sol and clean lint free rags. Why is that? I thought lacquer thinner was the best thing to use since it dissolves grease well and dries quickly with no residue (visible residue anyway).

Lacquer thinner, acetone, MEK, and enamel or urethane reducers are NOT surface cleaners. Lacquer thinner evaporates too fast and doesn’t give you time to wipe it off wet. It is also much to strong a solvent for most cleaning and can get under the edges of sand thrus or soften substrates. Enamel and urethane reducers often have resins and other components in them that are designed to be added to the product they were INTENDED to be used with.

Rich, you should use a wax grease remover prior to paint. A gallon of PPG's DX330 is around 20 bucks, it will last throu several cars!

Now what PPG products you spraying? I looked throu my tech sheets and didnt see any RTS(Ready To Spray)Epoxy.
The only 1 step black paint from PPG I can think of is ST1202, which is a flat black paint made for industial coatings.

If I know the product numbers I can tell you how they spray and if reducing is a good idea or not...Eric

The other guys have given you some good and technically correct information. I won't disagree with them.......
...however...

I have painted many engines and chassis parts by cleaning the oil/grease off as best I could, then use a siphon feed gun with the fan control screwed all the way in and literally wash the engine or part with lacquer thinner. To properly clean a tanked engine or new engine requires 1-2 quarts of lacquer thinner top to bottom and takes about 10 minutes.

I've done several engines, both rebuilds and new crates, and the only failure I had was an intake manifold that was cleaned in a new(at the time) hot water type parts cleaner. It began peeling after about three years.
I have a 72 Monte Carlo that I rebuilt the engine in 1988. It had been tanked and I did the lacquer thinner wash and painted it with DuPont Imron with NO PRIMER. It looks just as good today as it did in 1988 except for the half dollar size burns at the carb crossover.

If it were my rear end housing, I would do the lacquer wash that I described and paint it. If I really wanted to be extra careful, I'd do the primer(epoxy or otherwise) and then paint it. I won't tell you that's the best way for YOU to do it.

Regardless of exactly how you do it, the key to adhesion is making sure the oil/grease/dirt is removed prior to applying primer or paint.

Originally posted by sevt_chevelle:
Rich, you should use a wax grease remover prior to paint. A gallon of PPG's DX330 is around 20 bucks, it will last throu several cars!

Now what PPG products you spraying? I looked throu my tech sheets and didnt see any RTS(Ready To Spray)Epoxy.
The only 1 step black paint from PPG I can think of is ST1202, which is a flat black paint made for industial coatings.

If I know the product numbers I can tell you how they spray and if reducing is a good idea or not...Eric The primer is an epoxy, the top coat isn't. The stuff is made to work together. The top coat must be laid down within three hours of shooting the primer from what they told me at the paint shop. The primer makes a good corrosion proof shield but it isn't UV proof thus the need for the top coat. It is a PPG paint, I don't recall the number. The label says flat black but they tell me it isn't completely flat, that it is similar to the GM Reconditioning paint. It had better be or they will have an irrate customer because I'll have to strip and repaint that axle!

The results were very good. I used no reducer whatsoever. I did clean the axle housing with lacquer thinner first to remove some traces of paint my wire wheel brush couldn't reach. I then cleaned the whole housing with a prep-sol type product of a different brand name. Read the details here:

http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=30;t=002928

It makes you feel great when things go the way you want them to, eh?

The respirator made the whole job fairly enjoyable. I could get pretty good with that paint gun if I had more practice. Soooo much better than working with spray cans.

My only error was mixing a bit too much primer (it's two-part so I couldn't save it once it was mixed) and that I had the air pressure too low while I shot the primer. It came out pretty slow and I had to shoot three coats to cover well. I caught the error before I started in with the color and it sprayed a whole lot better. I may have ended up getting a little more thickness to the primer than I really wanted, but the housing sure looks purdy!