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I think those blisters were just oil entrained in the metal itself
when our outside contractors repair / weld aluminum oil coolers they are always bake first to drive any oil out from the pores of the metal itself; solvents alone just don't cut it...
The magnesium valve covers are notorious for holding in solvents and oils.
some good info coming out here.
here is what i did.
both treated with paint stripper, pressure washed. both covers turned a dark grey, some sort of reaction eith the metal.
then,
emblem cover: took dremel and mostly/lightly/almost got all spots went over with the steel brush. worked great but didnt last long before it disintegrated. finished as best i could by hand.
passenger cover, hand sanded. lots of the grey "oxidation" left on the covers but it was smooth do i was like meh.
i painted both at the same time and the first pics wre of the driver side.
check out this one!
the non wire brushed side was waaaaay worse. <br/><br/>ill mouse sand it, bake it, isopropyl alch, re bake, then paint.
IMHO the porosity of magnesium is the problem.
I polished mag hubs then clear coated them with 2 stage to stop oxidation. No blisters but the mag turned gray under the clear coat in 6 months.
Doubt you will eliminate blisters using rattle can paint on magnesium. SWAG, 2 stage epoxy primer should seal the covers then color coat. No guarantees but the 2 stage clear I used on mag did not blister. No pre heating or baking.
both treated with paint stripper, pressure washed. both covers turned a dark grey, some sort of reaction eith the metal.
then,
emblem cover: took dremel and mostly/lightly/almost got all spots went over with the steel brush. worked great but didnt last long before it disintegrated. finished as best i could by hand.
passenger cover, hand sanded. lots of the grey "oxidation" left on the covers but it was smooth do i was like meh.
i painted both at the same time and the first pics wre of the driver side.
the non wire brushed side was waaaaay worse. <br/><br/>ill mouse sand it, bake it, isopropyl alch, re bake, then paint.
I believe you had good intentions BUT once you removed paint, pressure-washed (maybe needed a hot/soapy first or after) and was ready to move forward you needed to have used an "adhesion promoter", then an "etching primer" and finally your color. To recover from where you're at I'd think will require a fresh start.
"JoeC" uses the etching primer but doesn't mention what his "chemical clean" is prior to the primer. I'd think a hot/soapy wash, then the pressure rinse (or reverse the rinse/wash), adhesion promoter, etching primer then paint etc.
There are various adhesion promoters out there but if you were to use any product that is based upon Alodine® and the parts were again taken to just the metal you'd be maybe better served. Short-cuts? I doubt there are any.
****Meant to mention - I believe your "HEAT" is way to HOT and you'll never be able to manage the "heat cure". At a controlled 200° maybe but I doubt I'd venture there, learn from your recent experience.
IMHO the porosity of magnesium is the problem.
I polished mag hubs then clear coated them with 2 stage to stop oxidation. No blisters but the mag turned gray under the clear coat in 6 months.
Doubt you will eliminate blisters using rattle can paint on magnesium. SWAG, 2 stage epoxy primer should seal the covers then color coat. No guarantees but the 2 stage clear I used on mag did not blister. No pre heating or baking.
Good luck
thnx all. appreciate the brainstorming.
something was gassifying with heat. so youe porosity comment here is imo probably correct.
i cranked up the heat on the first one, no additional blisters formed. i have sanded, isopropal wiped, re baked before paint, in case the isopropal seeped into the pores, (baking now) and will hit with paint later today.
my particular status, oil company owner with shut in wells, makes free cash non existant, so im going about this in a cash strapped sort of way and do acknowlegde there are better ways.
im confident my 40$ fix will work. just need to get rid of thr volatiles in the porosity. where i live, in canada, powder coat on my valve covers was quoted at $450. lol.
You do know gas grills can cause drying paint to bubble right?
Gas cooking/grills make water vapor when they burn the gas.
aware of co2 h2o byproduct however would that affect the paint from underneath?
the other thing i did in round 2 here, is crank my water heater to max, and "clean" the valve covers in the dishwasher. i put a few drops of dishwasher soap in, and let it run. i thought it would heat it up a bit, wash away any oils. i wiped it off, stuck it on the bbq. (where it is now) and will let cool down and hit with pint later.
ant. good thought on the oil from the grill. i dont see it affecting from the inside out though. there was no discoloring that we might expect if the contaminents were from the outside in.
if this does work and other emulate in the future, i put in about 1/8th a cup of dawn dishsoap and ran into this problem. a few drops is alllll u need hahaa.
Last edited by VikingTrad3r; 02-09-2016 at 11:37 AM.
You heat it before you paint Crowz water mixing with past cooking.
dish washers don't use that kind of soap at least the floor got cleaned.
first time around i did not pre heat.
yah. wife wasnt home so all good.
after mouse sanding the second one, washing it on the dishwasher, then baking in oven to see if anything would come out, i opened up the bbq which i cranked to 400f and low and behold i found a "pore" bubbling old engine oil out of it. pic below. i think we found the culprit. the first set is already repainted and im hitting that one pore with isopropal after cooling down and ill repaint this second one.
i painted it when it was lightly still warm. hoping that as it cooled it might suck paint into the pores. doubful, given it will have already hardened but w/e.
after mouse sanding the second one, washing it on the dishwasher, then baking in oven to see if anything would come out, i opened up the bbq which i cranked to 400f and low and behold i found a "pore" bubbling old engine oil out of it. pic below. i think we found the culprit. the first set is already repainted and im hitting that one pore with isopropal after cooling down and ill repaint this second one.
i painted it when it was lightly still warm. hoping that as it cooled it might suck paint into the pores. doubful, given it will have already hardened but w/e.
thanks for posting this; some people will not believe that metal can have "pores" or that oil, etc. can be absorbed into metal, but seeing is believing
thanks for posting this; some people will not believe that metal can have "pores" or that oil, etc. can be absorbed into metal, but seeing is believing
my pleasure! i absolutely believe that there is a way to sand/strip/repaint these for a fraction of what a new landed set costs.
get aload of this set! (not for 85's but u get the drift!)
wtf!
87-91 Corvette Magnesium Valve Covers with Gaskets on Kijiji http://www.kijiji.ca/v-engines-and-engine-parts/nanaimo/87-91-corvette-magnesium-valve-covers-with-gaskets/1138897797
Had mine powder coated tyhree years ago. look great easy to care for.
Redid mine on the 85 Z51 and the finish paint was wrong color to light grey so I have 2 cans of the Spruce brand paint it is nickel silver going to just re top coat them and while torn down going to install new AIR pump damb thing has started making noise when engine warms up.
Where in OH are you I am in East Kentucky, we need to try to get a group together for a run!
Redid mine on the 85 Z51 and the finish paint was wrong color to light grey so I have 2 cans of the Spruce brand paint it is nickel silver going to just re top coat them and while torn down going to install new AIR pump damb thing has started making noise when engine warms up.
Where in OH are you I am in East Kentucky, we need to try to get a group together for a run!
North east corner. Youngstown area. Hoping to make the NCM in April. Love my C4. Been tring to get toNCM for years but something has always come up (so far). Maybe this year
I'm doing this project now as well. Mine are very corroded. I used stripper on them, sandblasted them, soaked them in Gunk Hydraseal II (they turned black), soap & water, re-sandblasted, wire wheeled, ground with Dremel, re-wire wheeled. Cleaned with lacquer thinner at various times during the process. I'm not a big fan of magnesium valve covers. This is a lot of work for very little longevity... because of the extent of the corrosion. I, too, was going to use etching primer but I haven't found any that is heat resistant. I don't think the run of the mill etching primer will stand up to engine heat.
I'm doing this project now as well. Mine are very corroded. I used stripper on them, sandblasted them, soaked them in Gunk Hydraseal II (they turned black), soap & water, re-sandblasted, wire wheeled, ground with Dremel, re-wire wheeled. Cleaned with lacquer thinner at various times during the process. I'm not a big fan of magnesium valve covers. This is a lot of work for very little longevity... because of the extent of the corrosion. I, too, was going to use etching primer but I haven't found any that is heat resistant. I don't think the run of the mill etching primer will stand up to engine heat.
I used eastwood's (gray) etching primer. no temperature related issues. from eastwood's technical data, the etching primer is good for 180 degrees. pretty sure the VC's don't get THAT hot -
Wow I've never seen blisters like that second one! I figured you might have put them on the grille too soon- I usually let stuff fully dry before I bake it otherwise I've seen a couple of blisters but nothing like that.
02-08-2016, 12:28 PM
