Zinc chromate and zinc phosphate outdrive primers

[lenny2113]

I painted my drive with zinc chromate primer. Went to buy another can for the second coat but they only had "zinc phosphate". Is there difference between the two of these primers?<br />Could I paint with zinc phosphate over zinc chromate?

 

[rybad]

Re: Zinc chromate and zinc phosphate outdrive primers

Thats really funny. I had the same problem. I painted my second drive with chromate. I guess I'll find out at the end of the season which is better. (you too!)<br /><br />-Dave

 

[sloopy]

Re: Zinc chromate and zinc phosphate outdrive primers

where are you buying your zinc chromate? Go to your local aircraft supply and buy a can of zinc chromate.

 

[Dunaruna]

Re: Zinc chromate and zinc phosphate outdrive primers

Zinc chromate is being phased out as it is carcinegenic, that's probably why you couldn't find it. Zinc phosphate is a good undercoat replacement but some people think it's not as good as the chromate. <br /><br />They are both undercoats. You could also use a good etch primer. Couple of good topcoats and your good to go.<br /><br />Aldo

 

[Boomyal]

Re: Zinc chromate and zinc phosphate outdrive primers

Originally posted by Dunaruna:<br /> They are both undercoats. You could also use a good etch primer. Couple of good topcoats and your good to go.

Aldo, are you saying that you should use an etching primer then zinc chromate? My local specialty paint store really played dummy when I asked about zinc chromate. <br /><br />I'm going to repaint both my outdrive and my intermediate housing. I have already glass beaded the original paint on my intermediate housing then over sprayed with the etching primer. Being inside the boat, the original paint was 90% intact with just a few places where it was down to the original lead based (red) primer and a few spots down to bare aluminum.<br /><br />My outdrive, however, has a lot of bare aluminum exposed. The specialty paint shop did say that the etching primer was the hot stuff, but maybe an overcoat of ZC would be good before the final 2 part polyurethane????<br /><br /><br />THE LOCAL OUTDRIVE GURU I USE HAD ZINC CHROMATE IN A SPRAY CAN WITH MERCURY MARINE WRITTEN ON IT. I ASSUME IT IS STILL AVAILABLE FROM MERC DEALERS.

 

[Dunaruna]

Re: Zinc chromate and zinc phosphate outdrive primers

O'k, I'll qualify my previous statement. Zinc Chromate is being phased out IN AUSTRALIA, I don't know about the U.S. It would make sense that the cancer causing part of the paint would be phased out universally but then when does anything in this world make sense?<br /><br />Zinc chromate and zinc phosphate are designed as undercoats for bare aluminium. Phosphate doesn't always adhere well (that's my experience anyway). I prefer to use an etch primer (which used to contain lead & chromate) then a coat of phosphate then two or three top coats.<br /><br />But boom, I no chemist, I don't know how chromate and phosphate would react if used together.<br /><br />Aldo

 

[Dunaruna]

Re: Zinc chromate and zinc phosphate outdrive primers

Just to add, your final undercoat will need to be compatible with the 2 pack poly.<br /><br />Aldo

 

[Boomyal]

Re: Zinc chromate and zinc phosphate outdrive primers

Originally posted by Dunaruna:<br /> Just to add, your final undercoat will need to be compatible with the 2 pack poly.

At least the specialty paint shop confirmed that the etching primer they sold me was compatable with the two part poly, so I guess I will stick with that. Thanks

 

[Dunaruna]

Re: Zinc chromate and zinc phosphate outdrive primers

I've just done a bit of googling, I found some sites that say zinc chromate is banned in some states, but not all. The following is from the OSHA - U.S. Dept. of Labor. There are many pages of information but this stands out.<br /><br />"The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for zinc chromate of 0.001 mg/m(3) as a TWA for up to a 10-hour workday and a 40-hour workweek. NIOSH considers zinc chromate a potential human carcinogen [NIOSH 1992]." <br /><br />2. Effects on Humans: Exposure to zinc chromate can cause irritation, tissue ulceration, and cancer in humans. Inhalation of dusts containing chromates causes irritation of the mucous membranes [Rom 1992]. Gastric distress, olfactory sense impairment, and the yellowing of teeth and tongue may also result from excessive exposures to chromates. If exposures are prolonged, ulcerations of the nasal mucosae may occur as well as possible septal perforations. Prolonged dermal contact may produce ulceration of the skin. The increased exposure that results from an ulcer may result in renal chromate toxicosis, liver failure or death [Rom 1992]. Ocular effects including eye lesions, conjunctivitis, and keratitis have been associated with exposures to chromates [Rom 1992]. Prolonged exposure to chromates can cause chronic bronchitis, rhinitis, or the growth of nasal mucosal polyps [Rom 1992]. Exposures may also lead to chemical pneumonitis. Chronic exposures to hexavalent chromium compounds can cause lung and gastrointestinal tract cancer including cancer of the esophagus, stomach, intestines, and pancreas [Rom 1992]. Of six studies that examined the association between exposure to zinc chromate and lung cancer, five were cohort studies and one was a proportionate mortality study [ACGIH 1991]. In four of the five cohort studies there were also exposures to lead chromates. All of the cohort studies demonstrated an association between exposure to chromates and lung cancer. It was noted that because of the compounded exposures with lead chromate it was not possible to separate out the effects caused by each individual chromate compound [ACGIH 1991]. IARC has concluded that there is sufficient evidence for the carcinogenicity of hexavalent chromium compounds to humans [IARC 1990]."<br /><br />Aldo

 

[BillP]

Re: Zinc chromate and zinc phosphate outdrive primers

Our local paint store rep told me ZC is better than PC so I used the zinc. ZC is still on the shelves in Florida and may be regulated like CCA pressure treating is. OK and legal for commercial use but not for private use...there is a new process for that. Don't know for sure but that may be why ZC is still available.

 

[lenny2113]

Re: Zinc chromate and zinc phosphate outdrive primers

I should have been wearing a mask while spraying zinc chromate... <br />In any case, has anyone ever used chromate as first coat and chromate as second coat of primer?

 

[crazy charlie]

Re: Zinc chromate and zinc phosphate outdrive primers

Lenny,use the phosphate.I have always found it to do a better job than the chromate anyway.Zinc chromate always seems to lift off.I have always opted for the phosphate and have never had the lifting problem with it.Sometimes limiting us to one choice turns out to be better.Charlie

 

[lenny2113]

Re: Zinc chromate and zinc phosphate outdrive primers

I will do an experiment. I already coated one coat of chromate for both drives, so chromate it will be for the second coat as well. <br />I will prime bellhousing with 2 coats of phosphate and finish off with 2 coats of anti-fouling drive paint. In fall, I will have my answer by comparing bellhousing condition and outdrive. <br />Thank you all!