# zinc phosphate primers



## Painter Dan1

Just wondering if anyone else out there has had any trouble applying the correct top coat to a zinc phosphate primer. I am using a kremlin airless air assited machiene with a zinc phosphate primer and a polyureatheane top coat. I have been told some poly top coats are not compatable with a zinc phos primer. I would like to no if any one has an idea why some aren't compatable and some are. I am a little bit miffed as to why some are and some aren't. I would ask my paint rep but i just think he is trying to constantly make a sale with us. Many thanks for all your help and input


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## MrPaint

Can you give me more information on what products you have had problems with? I have some ideas that might help but I don't wanna ramble without the proper information.


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## robladd

I would ask the manufacturer if the top coat your intending to apply to the primer is compatible.

I try to get a coating system that the manufacturer recommends. If not your setting your self up for failure. Why take a chance?


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## Painter Dan1

previously we have been using HMG zinc phosphate high build primer with a HMG poly top coat 1k had good results in the short term but we have had several machiens back with very bad top coat adehesion in some cases nearly all the top coat has peeled off. We have now changed paint suppllier to PRONTO and still with the same system (zinc phosphate high build and 1k poly top coat) we have used this system for 4months and so far no top coat adhesion issues but we are still in the short term??????. The problem we have is we are thinkin that the previous paint supplier has either miss sold us in the past or he just dont have a clue what he is on about. Obviously with the machiens that have come back there is a cost issue of about £3000-£5000 to take them apart blast re-paint and then back together this is why we need to no exactly where the problem is thank you for all your help.


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## CApainter

Painter Dan1 said:


> previously we have been using HMG zinc phosphate high build primer with a HMG poly top coat 1k had good results in the short term but we have had several machiens back with *very bad top coat adehesion in some cases nearly all the top coat has peeled off*. We have now changed paint suppllier to PRONTO and still with the same system (zinc phosphate high build and 1k poly top coat) we have used this system for 4months and so far no top coat adhesion issues but we are still in the short term??????. The problem we have is we are thinkin that the previous paint supplier has either miss sold us in the past or he just dont have a clue what he is on about. Obviously with the machiens that have come back there is a cost issue of about £3000-£5000 to take them apart blast re-paint and then back together this is why we need to no exactly where the problem is thank you for all your help.


So this seems that the top coat is delaminating from the primer. How well is the primer adhering to the steel substrate? If the primer is adhering well, then it could be that you are applying the top coat in too long of a period between the primer, or too soon and not allowing the solvents to evaporate in the primer, which would actually cause wrinkling rather then delamination.

Alkyd primers that are left to dry too long in between top coats can result in delamination of top coats due to the hardening process that takes place as soon as the alkyd begins to oxidize with the atmosphere. The drying oils in these products are actually forming a film through the chemical change of oxidation. The longer the exposure the harder they get, and therefore require sanding in between coats


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## MrPaint

What is the timeframe between the parts receiving primer and topcoat? Have you run any adhesion tests on the new or old system using ASTM-D3359? It's an extremely easy test to do and can give you some idea of what you are dealing with.


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## mustangmike3789

Painter Dan1 said:


> Just wondering if anyone else out there has had any trouble applying the correct top coat to a zinc phosphate primer. I am using a kremlin airless air assited machiene with a zinc phosphate primer and a polyureatheane top coat. I have been told some poly top coats are not compatable with a zinc phos primer. I would like to no if any one has an idea why some aren't compatable and some are. I am a little bit miffed as to why some are and some aren't. I would ask my paint rep but i just think he is trying to constantly make a sale with us. Many thanks for all your help and input


this is some info that i found in SSPC painting system guide NO.8.00 guide to topcoating zinc-rich primers 4.2 selection of topcoat.
"when topcoating zinc-rich primers,consideration must be given to the fact that zinc is being coated, not steel. coatings based on drying oils, such as most oils and alkyd types, tend to react with the zinc metal to form zinc soaps,resulting in loss of adhession and peeling of the top coat. in general, coatings that have poor alkali resistance should not be applied directly to zinc-rich primers. coatings with oil-containing vehicles such as oil paints, alkyd enamles, vinyl alkyds of the oxidizing type,long oil silicon alkyds, and epoxy esters should not be applied directly to zinc-rich primers.
polyurethane- some formulations can be applied directly; others require a tie-coat.


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## MrPaint

mustangmike3789 said:


> this is some info that i found in SSPC painting system guide NO.8.00 guide to topcoating zinc-rich primers 4.2 selection of topcoat.
> "when topcoating zinc-rich primers,consideration must be given to the fact that zinc is being coated, not steel. coatings based on drying oils, such as most oils and alkyd types, tend to react with the zinc metal to form zinc soaps,resulting in loss of adhession and peeling of the top coat. in general, coatings that have poor alkali resistance should not be applied directly to zinc-rich primers. coatings with oil-containing vehicles such as oil paints, alkyd enamles, vinyl alkyds of the oxidizing type,long oil silicon alkyds, and epoxy esters should not be applied directly to zinc-rich primers.
> polyurethane- some formulations can be applied directly; others require a tie-coat.


Saponification? I thought we were dealing with a "poly" topcoat? If its a polyurethane modified alkyd or quick dry enamel, I agree with you 100% but if it's a moisture cured urethane or similar product it's probably something quite different.


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## robladd

Painter Dan1 said:


> previously we have been using HMG zinc phosphate high build primer with a HMG poly top coat 1k had good results in the short term but we have had several machiens back with very bad top coat adehesion in some cases nearly all the top coat has peeled off. We have now changed paint suppllier to PRONTO and still with the same system (zinc phosphate high build and 1k poly top coat) we have used this system for 4months and so far no top coat adhesion issues but we are still in the short term??????. The problem we have is we are thinkin that the previous paint supplier has either miss sold us in the past or he just dont have a clue what he is on about. Obviously with the machiens that have come back there is a cost issue of about £3000-£5000 to take them apart blast re-paint and then back together this is why we need to no exactly where the problem is thank you for all your help.


I checked out Pronto's web sight. Are you using 310:006 for priming and 308:200 for top coat. That's their recommended coating system and if it's lasted 4 months
without problems. I would stay with thus system.


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## optimal

Zins is a tricky product to work with. Here is a good thread to read on. Are you working with an inorganic or organic product. Inorganic is tricky, you need to have proper cure time and should Waite at least 24 hours prior to topcoat and should thin down your topcoat and apply a mist coat before a full coat. Also you topcoat needs should be high solids. So a high solids poly or a high solids epoxy. Just two weeks ago we used zinc clad 2 and topcoated with macropoxy 646 fast cure. We waited over 48 hours to topcoat and thinned our macro 30 percent for a mst coat and applied a full unthinned topcoat.

http://www.rustbullet.com.au/techni...g-systems/guide-to-zinc-rich-coating-systems/


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## oz_painter

CApainter said:


> So this seems that the top coat is delaminating from the primer. How well is the primer adhering to the steel substrate? If the primer is adhering well, then it could be that you are applying the top coat in too long of a period between the primer, or too soon and not allowing the solvents to evaporate in the primer, which would actually cause wrinkling rather then delamination.
> 
> *Alkyd primers that are left to dry too long in between top coats can result in delamination of top coats due to the hardening process that takes place as soon as the alkyd begins to oxidize with the atmosphere. The drying oils in these products are actually forming a film through the chemical change of oxidation. The longer the exposure the harder they get, and therefore require sanding in between coats*


when we use zinc prime over here we make sure we apply the top coat within 2 weeks otherwise the zinc primer dries to hard and the top coat will generally de laminate


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