Primer Problems

[Welding man]

What is the best type of primer to use on a tractor. I am haveing a lot of problems getting the primer to stick on the main body of the tractors(engine -transmission -etc.) due to the old oil soaked castings. We steam clean two or three times-have used oven cleaner-washed down with laquer thinner etc.I have tried etching primer- urethane primer- and acrylic primer -poly satin sealer -nothing sticks-I usually paint with PPG omni acrylic enamel with hardner on the main body. I am at a loss on what to do next. Any help woud be greatly appreciated.

 

[Rod (NH)]

Hi,

Here are my suggestions:

1. Lose the lacquer thinner for a surface cleaner. It dries too fast to do a decent job. Get a real metal cleaner designed for the purpose - like PPG's DX330. Learn how to use it properly <a href="http://www.autobody101.com/articles/article.php?title=Surface%20Cleaners">here</a>.

2. Lose the etching primer. Epoxy is a much better choice, especially for porous castings. Since you are already using a PPG OMNI product for a topcoat, PPG's OMNI MP170 would be an excellent choice for an epoxy primer. Epoxy also has better adhesion characteristics than other primers. Urethane primers are generally not used directly on bare metal if you want the best adhesion and corrosion protection. Acrylic primers are old technology and also are not the best for direct to bare metal. Epoxy is the absolute best choice.

3. If using oven cleaner or other chemical stripper, do a through pressure wash with water afterwards and allow a abundant amount of time for drying before using the surface cleaner. Also allow a abundant amount of time for complete drying in the pores of the castings after the surface cleaner and before the epoxy primer.

Rod

 

[Welding man]

Thanks for the info, I will try your suggestions on my next project,very soon. thanks again.

 

[GordoSD]

The DX330 is a metal prep product. Use it to condition somewhat rusty metal. It has phosphoric acid in it for cleaner.It does not remove oil or grease.
After using it you should use a oil remover. Body shop supply houses sell it. One brand name is "Prep-sol

Now that the rust is off, the oil is off go ahead and shoot it with the epoxy primer.

Gordo

 

[Welding man]

Prep sol only makes matters worse -its no better than mineral spirts, Cast iron soaks it up like a sponge.

 

[Rod (NH)]

DX330 does NOT contain phosphoric acid. It's a surface cleaner, aka a wax and grease remover, NOT a metal "cleaner" treatment in the sense you are talking. You probably have it confused with DX579, a true metal cleaner that does contain phosphoric acid. DX579 is not the appropriate product for the OPs use.

Rod

 

[Rod (NH)]

If you don't like DuPont's Prep Sol, you probably won't like PPG's DX330 either since they are similar products that provide a similar function. Most surface cleaners, aka wax and grease removers, are derived from mineral spirits or have mineral spirits as components.

Rod

 

[GlenIdaho]

Rod is correct concerning DX330. I use and it works good. Here's some info on PPG wax and grease removers taken from their site.

"PPG DX Cleaners are specifically designed to remove wax, grease, silicones, road tar, engine oil, overspray, adhesives and other contaminants. DX320 - Fast Evaporating Cleaner · DX330 - ACRYLI-CLEAN® · DX394 - 1.4 Low VOC Cleaner · DX440 - DITZ-O® Wax & Grease Remover"

 

[CNKS]

Rod is correct. I have used DX 330 and the stronger DX 440 for years with excellent results.

 

[CNKS]

If you are looking for the rags to come away clean using wax and grease removers on cast iron, they will be clean after about 20 applications. Don't worry about it. Use oven cleaner and pressure wash to get rid of most of the grease. Then use wax and grease remover 4-6 times and call it good. Cast is next to impossible to get perfectly clean.

 

[glennster]

like the other guys have said, cast isnt the easiest to get clean and ready for paint. what i have been doing that has been working at least for me, after the paint is stripped off, whether by chemical or mechanical means, pressure washing or steam cleaning is next, then i use a product made by castrol called super clean, napa sells it, purple jug. spray it on, let is sit for 20 minutes or so, the rinse it off with water. i prefer hot water, it drys quicker than cold. when you are happy with that, my next step is to use an old spray gun, load it with inexpensive lacquer thinner. you can get 5 gallon cans of gun cleaning grade thinner fairly cheap. turn the air pattern adjsutment all the way in for a tight pattern, then wash the cast with lacquer thinner. start at the top and work down. you will see the grease and oil come out and flow down. do that couple times. last step is load the gun with pre-cleano, prep sol, 900 wax and grease remover(what ever your preference) and repeat. at this stage, dont use a rag on the castings, it will leave lint hairs stuck to the cast. wash down until no more oil film discolors the prepsol, then you are ready for primer. cleaning and prep work is 90% of a good paint job.

 

[DickL]

I was told many years ago to never use primer on cast iron. I don't and never had a pealing problem. Started painting cast iron molding machines back in the early 1960. I was told this by a factory rep for HPM. I have put rattle can primer on engines that just came from a hot tank and it has not came off.
I have had good luck with the wifes Dawn and a stiff brush as a final cleaning.

 

[GordoSD]

You are right My Bad. I keep the 579 on hand to treat old parts prior to the "Prep Sol" application.The "Prep Sol" is as good as the 330 but cheaper.
Glenster, is that gun cleaning grade laquer thinner cheaper than the stuff at ChinaMart? My ABS guy never told me about it?

Gordo