Another lesson learned the hard way

[RR_Mel]

After reading a post on a forum I used Rust-Oleum Self Etching Primer on a brass SD9 diesel shell several years ago and it worked very good.  The paint is still tough as nails.

 

I bought a couple of clunker Hobbytown of Boston E7s off eBay and stripped the shells in Denatured Alcohol.  The Hobbytown shells are cast white metal so I decided to prime the metal with the Self Etching Primer because it had worked so well on my SD9. The primer had set on the shelf for 5 or 6 years so I tossed it and bought a new can.

 

The primer went on very nice.  I let the two metal shells cure two days before I airbrushed them with Tru-Color Paint.  I let the TCP Daylight Red cure for another two days then masked them and shot the Daylight Orange stripes.  When I removed the masking tape big chunks of paint and primer came off with tape.

 

I let the shells set for two weeks and give it a second try thinking it hadn’t completely cured.  I taped the E7A today to shoot the Aluminum striping and this is what happened when I removed the tape.

 

 

 

I’ve been using both TCP and the 3M tape for over two years without any problems so it must be the combination of the Rust-Oleum Primer.    

 

Evidently the Self Etching Primer won’t work on white metal.

 

Another lesson learned the hard way, I will stick with what has worked in the past and not use Self Etching Primer again.

 

I’m open for comments, positive and negative.

 

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[carl425]

RR_Mel

I’m open for comments, positive and negative.

Join me in modeling the N&W in the mid 70's.  Plain black paint - no masking required.

If it's any consolation, it looks like you had done a nice job on the paint.  But then I suppose that just makes it more aggravating when it gets screwed up.

BTW, when I do use masking tape, I always use my heat shrink gun to soften the adhesive before peeling it off. (not that I think that would have prevented your problem)

[cprfan]

I had a client request I paint a Cary A-B Set of F units. I had similar problems. I purchased a cheap grit blaster and gave the shells a blasting. This, combined with very careful cleaning with vinegar and then rinsing well with distilled water gave me success. I was painting the old CNR Green and Yellow scheme.

[dstarr]

I always etch metal (brass, Zamak, pot metal) before painting.  A 1/2 hour soak in supermarket vinegar works for me.  The mild acid etches the metal and gives the primer some tooth to grab onto.  Also degreasing is critical, the thinnest film of oil, mold parting compound, or fingerprints will spoil a paint job.  For serious work wear rubber gloves after the last wash with dish detergent and hot water rinse.  I haven't tried the "self etching" primers.  I use Rustoleum or Krylon "auto primer" which comes in rattle cans of light gray, dark gray and red.  For that top coat, I would use the red auto primer.  The auto primers have all the chemistry the paint company knows to make them stick to metal, in fact I've seen 'em stick to moderately oily auto parts.  If your metal is good and clean, they will stick better. 

[mlehman]

Vinegar!

That must've been a bummer, Mel.

[wjstix]

I've used zinc chromate (rustry red color) paint as a primer on metal engines (old Mantua boilers, Cary metal body shells) with good results. Put that down as a first coat, then paint 'normal' gray primer over that. 

BTW it's also a good match for UP's standard freight car color.

[zstripe]

Mel,

Looks to Me like the primer stuck well...the TCP paint seems like it didn't stick. Did You scuff the primer at all, before Your dust coat....You did start with a dust coat right? If You didn't that is part of Your problem. Any paint that comes of with masking did not adhere correctly to begin with. Also a fine 3m scuff pad would have helped. I mix Acryl paints and solvent all the time 1:1 and models and always scuff primer before dust coat, which is also important, if the other coats are to stick. I use 3m fine line tape when masking colors.....but I only burnish the edge where the fine line needs to be and just press on the other. I use Blue painter's tape to tape the rest on half the fine line tape, that just lightly pressed on. Of course for larger jobs, You would use masking paper.

The pic' is a Ulrich cast metal tanker and tractor that I used the same procedure as I explained above. Just washed the castings well and applied Floquil reefer white, which is very flat on first, dust coat, finish coat. Fine line tape, then yellow, which is Model master enamel, let sit three days and taped and put on the Red, MM also. After it set for a few hours I carefully removed the masking, peeling at an angle toward the seam, not away from it.

Take Care!

Frank

 

[RR_Mel]

Well Gentlemen I was able to patch it.  Because the tape didn’t pull off the paint above the silver I took a chance and taped it again.  I retouched the bad spot after moping it with a Q-tip soaked in Acetone.  I only left the tape on the old paint for about 45 seconds hoping it wouldn’t stick to the paint enough to pull any off.

 

 

The bottom of the pilot will be an easy fix later.

 

I’ve tried everything you guys suggested over the past 30 or so years I’ve been using a airbrush and it all works.  Thanks for the all the input!  I was lucky this time.  I’m going back to what I know works.  I’ve been using Rust-Oleum and Krylon Automotive primer for years without any problems.  It works great and a light coat doesn’t ding detail.

 

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[RR_Mel]

zstripe

Mel,

Looks to Me like the primer stuck well...the TCP paint seems like it didn't stick. Did You scuff the primer at all, before Your dust coat....You did start with a dust coat right? If You didn't that is part of Your problem. Any paint that comes of with masking did not adhere correctly to begin with. Also a fine 3m scuff pad would have helped. I mix Acryl paints and solvent all the time 1:1 and models and always scuff primer before dust coat, which is also important, if the other coats are to stick. I use 3m fine line tape when masking colors.....but I only burnish the edge where the fine line needs to be and just press on the other. I use Blue painter's tape to tape the rest on half the fine line tape, that just lightly pressed on. Of course for larger jobs, You would use masking paper.

 

Thanks Frank

 

I did scuff the primer and I use the same tape you suggested.  I didn’t scuff the patched area after I mopped it with Acetone, too touchy.

 

After I started using Tru-Color Paints I’ve found I can tape over fresh paint in three hours without any damage.  I have switched over to 3M tape for everything.  The wide Delicate Surface Painters tape is the best masking tape I’ve ever used, it never bleeds or pulls up paint.  This was the first time I’ve had problems in many years, It has to be something about the Self Etching Primer.

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[dinwitty]

you want a low tack tape.