International Etch Primer

[freewilly]

Does any one know of any nasty effect that International Etch Primer might have on SG Iron or steel(s275) that I should look out for.

Cheers guys

 

[kenvlach]

Can you give a specification or the composition of International Etch Primer?

 

[freewilly]

Sorry it took so long, I would say I'm rushed off my feet but I think I lost them last week because they couldn't keep up with me.

The etch primer base contains: Butanone, propan-2-ol and zinc oxide. The etch primer curing agent conatains: Butan-1-ol, butanone, phosphoric acid and propan-2-ol.

All details can be found on

http://www.yachtpaint.com/UK/

look under primers - International etch primer.

Cheers you any help you can give.

 

[kenvlach]

freewilly,
I looked up the etch primer composition. There should be no problem with adverse reactions, as phosphoric acid-based solutions (including alcohol & other organics & zinc) are commonly used on steel and iron for
1) acidic cleaning (phosphoric acid, organic solvents, acid-stable detergent & wetting agents),
2) wash primers (phosphoric acid, polyvinylbutyral resin and zinc chromate pigment): DOD-P-15328 and MIL-P-8514,
3) combination cleaning/pretreatment of steel surfaces (including cases where some surfaces are Zn or Al) prior to painting. Federal spec. TT-C-490 (multiple solutions mentioned, refers to other specs.) and
4) pretreatment & rust removal prior to painting: MIL-C-10578. “This specification covers five types of concentrated phosphoric acid corrosion removing and metal conditioning compound which, when diluted with water and applied to metal surfaces, will remove rust from ferrous metal surfaces and provide a slight etching action for ferrous and nonferrous metals to promote the adhesion of paint or corrosion preventives.”

International Etch Primer (2-part):
Ingredient EINECS Concentration
Butanone 201-159-0 25-50
Propan-2-ol 200-661-7 25-50
Zinc oxide 215-222-5 02.5-10

Ingredient CAS Number Concentration)
Butan-1-ol 000071-36-3 50.00 - 100.00
Butanone 000078-93-3 10.00 - 25.00
Phosphoric acid. 007664-38-2 2.50 - 10.00
Propan-2-ol 000067-63-0 25.00 - 50.00

from

http://www.yachtpaint.com

The application notes for the etch primer state “Colour changes from a bright yellow/ochre to a dull yellow/ochre indicating successful etching.”

I believe this is due to a change in pH, when the low pH phosphoric acid is neutralized by reaction with the surface, leaving a neutral pH phosphate. I note that TT-290D, paragraph 6.11 mentions “Alcoholic phosphoric acid and phosphoric acid containing a solvent and detergent (method VI) discolor the surface.”