Can't Shake It - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
User Tag List

Reply
 
LinkBack Thread Tools
post #1 of 43 (permalink) Old 09-11-2018, 07:33 PM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
Can't Shake It

In spite of my desperate (and repeated) attempts, my rust repairs keep rusting. What am I doing wrong?

All,
It's been awhile since I've posted (been enjoying driving the Z instead of talking about her), but I'm experiencing a rust problem that I'm unable to solve. I'm repairing relatively small (mostly surface) patches of surface rust on body panels, but the rust keeps returning.....and often within just a few days of the completion of the repair. In a nutshell, here's what I'm doing (see if you can spot the problem.....PLEASE, I'm getting desperate!!):

1) Grind/sand rust down to bare, rust-free metal.
2) Clear area with denatured alcohol. Let dry.
3) Apply metalized Bondo and let dry (hard) ~30-45 minutes.
4) Sand to shape to body panel.
5) Mask and apply two coats of primer recommended by (and came from) paint company, waiting ~10~15 between coats.
6) Sand surrounding repair area with 180 to blend repair edge to surrounding finish.
7) Apply light glazing layer and, when dry, sand with 400 to smooth/blend.
8) Wet-sand area with 600 to blend and prepare surrounding area to accept base colour coat.
9) Clean with tack cloth.
10) Apply several light layers of base colour coat, waiting ~10~15 between coats.
11) After base colour coat's dry (~45 minutes), wet-sand with 1200 and 1500.
12) Apply two coats of clear coat, waiting ~10~15 minutes between coats.
13) Wait 48 hours and wet-sand with 1200 and 2000, then compound and polish.

When done, the area looks nearly OEM. But within a few days, I'm getting rust bubbling under the paint again. What gives?
Am I doing or using something wrong?


Last edited by freddy333; 09-11-2018 at 07:47 PM.
freddy333 is offline  
Sponsored Links
Advertisement
 
post #2 of 43 (permalink) Old 09-11-2018, 07:37 PM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
Materials:
freddy333 is offline  
post #3 of 43 (permalink) Old 09-11-2018, 09:07 PM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
For some reason, the photo links aren't appearing...
freddy333 is offline  
Sponsored Links
Advertisement
 
post #4 of 43 (permalink) Old 09-11-2018, 09:08 PM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
Since the original pics don't see to be attached, here's an example of what the repairs look like after a few days...
freddy333 is offline  
post #5 of 43 (permalink) Old 09-12-2018, 02:21 AM
Senior Member
 
Join Date: Sep 2006
Posts: 5,079
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 149 Post(s)
Just a wild-ass guess here but the additives to denatured alcohol to make it poisonous, like MEK or pyridine, are water soluble and may be leaving behind a film that attracts moisture in the air and reacts with the metal under the bondo. .......Use acetone or lacquer thinner and/or some phosphate "rust buster", excess wiped off with a damp cloth, to temporarily protect the surface.

zippityzda
dumbestone is offline  
post #6 of 43 (permalink) Old 09-12-2018, 03:56 AM
Senior Member
 
Join Date: Jul 2013
Location: Palmetto, GA
Posts: 123
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Garage
There are a couple of possibilities that come to mind.
1. You are never truly getting rid of all the rust. Sanding and grinding usually won't do it as it resides in the tiny pits that come along with the rust.
I would use some type of rust dissolver/neutralizer like Krud Kutter or similar. It takes multiple applications most times. Once you are sure you have it all, paint the area with a good quality 2K epoxy primer.
2. The bubbling is not rust but outgassing from solvents in the primer or the filler not curing properly.

What primer and what filler are you using? I like to get all of that type stuff from an automotive body supply house along with the data sheets and whatever info I can get out of the counter guy about proper cure times, compatibility issues and etc.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Greg Reid is offline  
post #7 of 43 (permalink) Old 09-12-2018, 09:18 AM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
Quote:
Originally Posted by dumbestone View Post
Just a wild-ass guess here but the additives to denatured alcohol to make it poisonous, like MEK or pyridine, are water soluble and may be leaving behind a film that attracts moisture in the air and reacts with the metal under the bondo. .......Use acetone or lacquer thinner and/or some phosphate "rust buster", excess wiped off with a damp cloth, to temporarily protect the surface.
I've had the same thing happen 8 or 9 times (different repair areas) now. At least once, I did use acetone instead alcohol (also tried Windex) and it was definitely dry, but the result was the same. Within a few days, bubbles appeared under the paint. Then, as additional days pass, the bubbles grow into a larger scab, forcing me to redo it. The area in the photo in the first post has been redone 6 times now! Each time the bubbles begin to appear within 72 hours and they start at different spots within the repair area. I don't know if any of you are seeing the photos I keep posting, but here's a link to the photo showing what the bubbles look like when they first appear 72 hours after completing the repair:
http://www.triumphpc.com/work/280zx/bubbles.jpg
freddy333 is offline  
post #8 of 43 (permalink) Old 09-12-2018, 09:31 AM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
Quote:
Originally Posted by Greg Reid View Post
There are a couple of possibilities that come to mind.
1. You are never truly getting rid of all the rust. Sanding and grinding usually won't do it as it resides in the tiny pits that come along with the rust.
I would use some type of rust dissolver/neutralizer like Krud Kutter or similar. It takes multiple applications most times. Once you are sure you have it all, paint the area with a good quality 2K epoxy primer.
The photo in the first post is of the last repair, where I applied the bondo right onto the bare metal. In most of the previous several repairs, instead of removing all the (visible) rust, I used one of three different "de-ruster" potions and left a bit of rust for the potion to react with (per the potion's instructions). They always bubbled within 72 hours. It was only after trying three different de-rusters that I figured the problem must be the de-ruster and/or leaving -some- rust behind. That's the only reason I did NOT use anything this time.
So far, the de-rusters I've tried are Loctite Extend Rust Neutralizer, Purple Power De-Ruster and POR-15 Black. And I'm one of those neurotic types (when it comes to the Z) who follows the instructions to the letter. Here's what the POR-15-treated area looks like today (it was finished 1 month ago and you can see the POR-15 under there...it's on the inside of the panel as well):
http://www.triumphpc.com/work/280zx/por15.jpg

Quote:
2. The bubbling is not rust but outgassing from solvents in the primer or the filler not curing properly.
What primer and what filler are you using? I like to get all of that type stuff from an automotive body supply house along with the data sheets and whatever info I can get out of the counter guy about proper cure times, compatibility issues and etc.
I'm not sure why my photo links don't show up, but here's another link to a photo of everything I used for the repair in the first post:
http://triumphpc.com/work/280zx/materials.jpg

Last edited by freddy333; 09-12-2018 at 09:51 AM.
freddy333 is offline  
post #9 of 43 (permalink) Old 09-12-2018, 09:37 AM Thread Starter
Senior Member
 
freddy333's Avatar
 
Join Date: Feb 2009
Location: DC
Posts: 1,448
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
(Thread Starter)
In case it's not showing up for you guys, here's another photo link showing the tiny bubbles that appeared 72 hours after completion of one of the two last repairs:
http://triumphpc.com/work/280zx/bubbles.jpg


This is the last repair, done two days ago. You may be able to see the first bubble along the edge of the wheel well:
http://triumphpc.com/work/280zx/lastrepair.jpg

Last edited by freddy333; 09-12-2018 at 09:47 AM.
freddy333 is offline  
post #10 of 43 (permalink) Old 09-12-2018, 10:58 PM
Senior Member
 
bificus's Avatar
 
Join Date: Sep 2010
Location: SC
Posts: 1,046
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 53 Post(s)
Garage
Quote:
Originally Posted by Greg Reid View Post
There are a couple of possibilities that come to mind.
1. You are never truly getting rid of all the rust. Sanding and grinding usually won't do it as it resides in the tiny pits that come along with the rust.
I would use some type of rust dissolver/neutralizer like Krud Kutter or similar. It takes multiple applications most times. Once you are sure you have it all, paint the area with a good quality 2K epoxy primer.
2. The bubbling is not rust but outgassing from solvents in the primer or the filler not curing properly.

What primer and what filler are you using? I like to get all of that type stuff from an automotive body supply house along with the data sheets and whatever info I can get out of the counter guy about proper cure times, compatibility issues and etc.



Agreed, I hearing good stuff about polyester primers and rust converter sprays these days.

1975 280Z F54/N47 MSA 6-1 Header 2.5 Exhaust
bificus is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



  Similar Threads
Thread Thread Starter Forum Replies Last Post
6 cars, 4 engines, 2 transmissions, 10 wheels, and more parts than you can shake a stick at..... zluster 90-96 Tech Discussion Forum 9 08-29-2007 07:59 PM
Shake, shake, shake Carrman 70-83 Tech Discussion Forum 8 05-31-2004 06:17 PM
shake shake shake... Von P 70-83 Tech Discussion Forum 4 05-20-2002 04:58 PM
shake in rear BRANDON 70-83 Tech Discussion Forum 1 08-18-2000 12:24 AM
steering shake joe240z 70-83 Tech Discussion Forum 4 01-12-2000 01:31 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome
 


Content Relevant URLs by vBSEO 3.6.1