self etching primer vs zinc chromate

[boater1234]

I am getting ready to paint up my outboard and wanted to know what would be better on it,zinc chromate or self etching primer?Which will protect better as well as giving the paint a better surface to stick to?

I have done tons of research the last few days and it's like 50/50 on all the sites i went on.What i did is sand down the whole lower unit to bare metal,i have read to use 50/50 water and vinegar for a better stick to begin with.I just recently painted the whole motor but put it on to thick and she peeled like an orange.This was my first time and i figured more was better but was i way wrong.I think i have the paint method down now as i think i was just in to much of a rush.

But now the thing is what primer to use on the bare metal and why?I have the good industrial yellow zinc chromate from moeller and i also have dupli colors self etching primer,so i have both to use.On the can of zinc chromate there is no drying times or recoat times so if i went that route what is the amount of time i should wait for it to be perfect to paint over?Should i sand it also?I'm painting a 15hp merc.I have the factory phantom black paint also.It was cheap at $6.50 a can so i got it for less then any other black i found.I want to do this right this time as i have spent tons of hours sanding and don't want to screw this up again.

Above the cavitation plate came out ok so i just sanded it down with 1000 grit paper to get any runs or minor bad spots out.I need to put one coat of paint on that,but like i said the main concern is the lower unit.I also wanted to know if clear coating is worth the trouble as all the sites were 50/50 on that also?The phantom paint is a high gloss so i would guess it would be a waste.Thanks for any info on the primer.

 

[JimS123]

Re: self etching primer vs zinc chromate

Since you're putting on rattle can paint it, if you use the motor a lot it isn't going to last more than a couple of years anyway. The biggest problems are scratch resistance and paint chipping.

In my experience if you use zn cr when you get a chip it'll be between the primer and the topcoat. If you use SE the weakest link is the bond between the primer and the metal. So, if you're in salt water maybe that matters to you.

Zn Cr is highly toxic, that's why its more of an industrial product as opposed to a DIY. If the can does not have application instructions, call the manufacturer's TS dept.

 

[Frank Acampora]

Re: self etching primer vs zinc chromate

The spray can clear coat tends to yellow with age. You will see that color change over a white or light finish, but not over the black. AND, I don't know if it will add any luster to the black either. So, the choice is yours. I would test it on the skeg, where it will wear off anyway, or on another piece of metal before you do the engine.

I did my first engine with a clear coat over a combination white and blue color scheme. Initially, I liked the results but after a couple of years, the white looks like cream. I no longer use a clear top coating and rely on a good surface finish and waxing

 

[RRitt]

Re: self etching primer vs zinc chromate

this is a tough question.

The first fork in the road is whether or not you are going to alodize the aluminum.
Alodine is a brand name for an aluminum conversion coating. It is the golden hue you see on many aluminum parts. It is some kind of chromic acid dip that converts the top layer of molecules into a different material that does not oxidize. That's why the golden parts still look new after 30 years. If you are going to alodize then your best coating for next layer is 2part (aka 2k) epoxy primer.

If you are not going to alodize then you'll need to etch the metal. Self etching primer (aka wash primer aka vinyl wash) is probably the best choice because it gives reliable and consistent results. Duplicolor makes a nice aerosol. PPG DX1491 is king. Your wash coat is suppossed to be as thin as you can possibly make it. For aluminum, it is trying to do the same thing as the alodine. cover the wash coat with a good 2k epoxy to get a waterprrof seal. For a mirror finish, go over the epoxy primer with a primer/filler. Primer filler has enough build-up that you can sand to a perfectly smooth surface without rubbing through. 320-400 wet dry sanding pad (thin sponge with silicone carbibe glued to one side) works very well for contoured surfaces.

Only consider zinc chromate if you are headed for saltwater. Otherwise the significant health hazard is not worth the minor gains.

Once you have that perfect subsrate then shoot the top coat of your choice. Dupont makes a superb 1step enamel that will probably outlive your boat. Follow directions on can, wear an approved mask, use a fan to create airflow.

 

[dingbat]

Re: self etching primer vs zinc chromate

There is a reason why they use ZN/CR primers on aluminum in industrial applications, it works.

Take it from someone who was hospitalized twice with ZN/Cr poisoning, you are not going to create health issue by priming the areas of bare metals of our outboard with ZN/CR. Wear a mask and use the it according to the directions on the can and you will be none the worse for wear.

If you bought OE Black Phantom, the paint is an acrylic lacquer. Make sure the primer that you use is compatible with lacquer coatings.
There is no need for a clear coat on top of a lacquer.

 

[JimS123]

Re: self etching primer vs zinc chromate

Now that you have more suggestions (and really good ones too) to totally confiuse the issue with yet more alternatives, let me throw another iron in the fire.......LOL.

The first motor I ever painted was back in the early 1970's. Back then I smoked and did all kinds of other bad things, so I didn't care about a little chromate. Boy it was nasty stuff though! I topcoated it with factory OMC paint, which back then was lacquer. Boy did it look good! Three coats total and it was done in a half hour. Hung it back on the boat a half hour later. Waited a day to buff it down and it looked factory new.

I still have the motor and even after all these years, the paint has held up perfect and has hardly a chip anywhere.

(PS - the post above came while I was typing. I didn't think any OEM outboard paint was lacquer any more. Surely, based on your past problems it doesnt sound like it is. But better find out for sure)

 

[Bob_VT]

Re: self etching primer vs zinc chromate

Keep in mind that it is a good idea to use vinegar, alodine then the zinc chromate but alodine is not available..... I would not sweat it ...... the cromate coating needs only be a good heavy dusting over the bare aluminum. There is no call to put it on thick at all........ when it is dry to the touch then paint it.

I would personally forget the rattle can clear over any of the paint........ rattle can clear coats are usually "hotter" and will lift and wrinkle MANY paints even of the same brand........ been there --- done that----- got the T shirt

Moving to restoration section

 

[kilowatts]

Re: self etching primer vs zinc chromate

Hi Guys:

I use the following method for painting all my MCM and Mercury parts with good success.

(i) Degrease with some kind of detergent and hot water, blow dry
(ii) Sand all existing paint. Sand to bare metal any chips, corrosion et.
(iii) Wash again with detergent and blow dry.
(iv) Wash with 50/50 white vinegar and water, blow dry.
(v) Shoot a thin coat of rattle can green ZC and let dry.
(vi) Shoot the first coat of black gloss Rustoleum and let dry.
(vii) Optionally sand between coats and apply last coat of Rustoleum. Use boat.

I have tried all the regular types of rattle can paint and I find Rustoleum to be the best and the cheapest. I don't have compressed air so I use my leaf blower to blow dry. It's usually enough to scuff up the existing paint if it's in reasonable condition as the factory is better at applying the finish than I am. I've used this system lots of times with good results. Good luck.

kilowatts

 

[kilowatts]

Re: self etching primer vs zinc chromate

Hi Guys:

I forgot to mention that I once had a boat painted by a professional with me acting as his laborer. He used a 2 part epoxy paint, I don't remember the brand. In my opinion the work and cost to prepare the boat and the shop, complete with HazMat suits was not worth the quality of the finish! The finish was excellent but i won't do it again. For engine parts, especially an outboard drive which will be exposed to salt water and goodness knows what else, the cheap and cheerful method works for me.

kilowatts

 

[boater1234]

Re: self etching primer vs zinc chromate

So you guys think rustoleum black is better then the factory paint?Will it hold up better?The factory paint is an enamel.Is rustoleum the same type of paint or better?Also it will be used 100% in saltwater.So i don't need much of the zc primer,thats the feeling i'm getting here.2 light coats,let it dry to the touch and paint.What i'm going to do is put 2 light to medium coats of black on let it cure,then see if there is any bad spots.If not i will put the final coat on after 24hrs as that is the cure time according to the paint can.If there is some bad spots i will wet sand down with like 1000 to 2000 grit sandpaper and then put one final coat on and be done with it.

Knowing it's a yellow primer that won't matter will it?It won't change the shade of black will it?When i was sanding it down the original primer was green like the duplicolor self etching primer i have.It sounds like zc is the favorite here.Also i will just back off the clear coat as it doesn't seem worth it.Also if anyone has anything else to add that might help me please do so,thanks for everyones help,this is awesome to me all the knowledge i have helping me as i would be lost like a dog without it.

 

[docrodg]

Re: self etching primer vs zinc chromate

Just to add another option...

ZC is great for salt water primer. Follow with VHT Exhaust paint, it is salt resistant and sticks great with no wear off. Painted a car frame with it and 10 years later frame is in perfect shape after driving on salted and sanded roads for 5 months each year without rinsing.

 

[jtw37]

Re: self etching primer vs zinc chromate

Fairly new at this boating thing, posting here and have the same idea about re-doing the finish. As I have a small Custom Powder Coating business, I thought that I would just powder coat all the metal/aluminum parts. EPA friendly, very minimal VOC's and wears like iron. Tuff and keeps looking good for a long time. Cleans easy and can be polished, so it will look good. Any thoughts on this? May even go faster.

 

[ezmobee]

Re: self etching primer vs zinc chromate

(i) Degrease with some kind of detergent and hot water, blow dry
(ii) Sand all existing paint. Sand to bare metal any chips, corrosion etc.
(iii) Wash again with detergent and blow dry.
(iv) Wash with 50/50 white vinegar and water, blow dry.
(v) Shoot a thin coat of rattle can green ZC and let dry.
(vi) Shoot the first coat of black gloss Rustoleum and let dry.
(vii) Optionally sand between coats and apply last coat of Rustoleum. Use boat.

I'd go this ^^^ route.

 

[JimS123]

Re: self etching primer vs zinc chromate

What i'm going to do is put 2 light to medium coats of black on let it cure,then see if there is any bad spots.If not i will put the final coat on after 24hrs as that is the cure time according to the paint can.If there is some bad spots i will wet sand down with like 1000 to 2000 grit sandpaper and then put one final coat on and be done with it.

The reason for starting and finishing the job within the 2 hour time frame is to ensure that all the coats of paint stick to one another. If you wait until after it has cured to put the final coat on, you'll have to sand it again, which is basically starting all over again.

Why don't you just look at it 5 minutes after you apply the second coat of black and see if there are any bad spots? If so fix it right then.

 

[wimpy 69]

Re: self etching primer vs zinc chromate

If using Alodine, be safe , very nasty chemical. Prep aluminum clean then an acetone wash before application.

 

[RRitt]

Re: self etching primer vs zinc chromate

So you guys think rustoleum black is better then the factory paint?Will it hold up better?The factory paint is an enamel.Is rustoleum the same type of paint or better?Also it will be used 100% in saltwater.So i don't need much of the zc primer,thats the feeling i'm getting here.2 light coats,let it dry to the touch and paint.What i'm going to do is put 2 light to medium coats of black on let it cure,then see if there is any bad spots.If not i will put the final coat on after 24hrs as that is the cure time according to the paint can.If there is some bad spots i will wet sand down with like 1000 to 2000 grit sandpaper and then put one final coat on and be done with it.

Knowing it's a yellow primer that won't matter will it?It won't change the shade of black will it?When i was sanding it down the original primer was green like the duplicolor self etching primer i have.It sounds like zc is the favorite here.Also i will just back off the clear coat as it doesn't seem worth it.Also if anyone has anything else to add that might help me please do so,thanks for everyones help,this is awesome to me all the knowledge i have helping me as i would be lost like a dog without it.

All saltwater?
that kind of settles it for me. I would uise alodine with epoxy.

you can mail order small amounts of alodine from aircraft spruce. I think its $10 for a quart. You can get good epoxy primers off ebay for cheap. Or you can drive down to a local auto body supply store and pick up a pint. Different solvents evaporate at different speeds. The local shop can sell you the solvent best matched to your local temperature and humidity.

IF you use rustoleum, then at least go to grainger or fastenal and buy the industrial grade. The hardware store rustoleum is a very crummy paint.

 

[boater1234]

Re: self etching primer vs zinc chromate

Ok now i'm getting a little confused on the rustoleum paint as a couple of people say it's good and then a person says it's crummy.Maybe i should just stick with the phantom black factory match.I have decided to use the zc yellow primer,i'm going to put 2 light coats on and then as jim said paint in one shot as it makes more sense to me as the paint will be some what tacky and stick to itself better.

I also like kilowatts idea,it sounds very good.The only thing is i kinda think it makes more sense like jim said to hit it at one time because it will stick better or i could be wrong.What i think i will do it shoot the primer,let it dry for an hr,then shoot 2 coats of (either phantom black,rustoleum black,or an epoxy black paint),wait for 24hrs and see how it turns out.If it comes out nice then that is all she wrote.Now i'm going to shoot my cowl to,what is the best paint for that?I went to autozone and got a clear primer from duplicolor called ahesion promoter which is suppose to be excellent for any type of paint.


SO I GUESS THE BIGGEST QUESTION NOW IS WHAT WILL BE THE BEST OVER ALL PAINT FOR THE MOTOR,AND COWL.I WANT IT TO LAST FOR SOME TIME BUT I'M ALSO LIMITED ON MONEY.ALSO I WILL USE SPRAY PAINT NOT A GUN IF THAT HELPS.

PHANTOM BLACK BY MERCURY
RUSTOLEUM BLACK
EPOXY BLACK FROM DUPLICOLOR OR ANY GOOD BRAND

 

[ezmobee]

Re: self etching primer vs zinc chromate

The report above is the first I've heard a generalized statement saying Rusto is crummy.

 

[JimS123]

Re: self etching primer vs zinc chromate

I reviewed the MSDSs and TDSs for Regular Rustoleum vs. the Industrial version and it looks like the better version may have a little more beef to it (higher binder content), but in my expert opinion the difference is not going to be significant, especially on a do-it-yourself job that is going to be stuck in saltwater. Over-the -counter Rustoleum is a fine product just as is.

I'm sure the OEM Mercury paint is no better or worse than Rustoleum.

Epoxy is the only way to go if you truly want it to last. So, go out and buy a pint of it, along with a compressor, paint spray equipment, respirator and spray booth. Then you will be able to put on a coat of paint equal to the factory.

You get what you pay for! If your economics preclude such a job, use what you have and stop fretting about it. Expect it to need recoating in 2 years, then spend 12 more bucks and do it over again. Part of the fun of having a boat is tinkering with it once in awhile.

 

[Yacht Dr.]

Re: self etching primer vs zinc chromate

Just me here..

I have done enough drives..

IMHO... Just me..for bare alum.

Alumiprep,Alodine,Zinc chromate, ( Prime and coat with your coatings..your cheap coating will account ).

I hope I didnt miss a step here.. ( this is pro ).

YD.