Editing Phosphoric acid as metal pretreatment

{{newarticle}}

The use of phosphoric acid-based products as metal pretreatments is controversial in hotrodding. Proponents favor its low cost and ease of use, while opponents cite the problem of acid film leading to topcoat failure.

==Brands of phosphoric acid-based metal pretreatments used for automotive work==
*[http://ospho.com Ospho]

==Reasons for using phosphoric acid==
*Inexpensive.
*[[Media blasting]] has its own set of drawbacks.

==Reasons for not using phosphoric acid==
*Metal pretreatment manufacturers are economically incentivized to recommend their products. A better point of view might be obtained from the manufacturer of the product that is destined to go on top of the pretreatment.

*Even a very low failure rate is economically disadvantageous, especially in light of the value of a professional paint job, and the labor required to fix a failure.

<blockquote>
''"Even though I believe I can use these products correctly I will not take such a risk when there are alternatives. It will only take 1 or 2 to put you out of business or in court."'' -- '''shine''', in [http://www.hotrodders.com/forum/ospho-factory-response-173513.html#post1234352 this post on the Hotrodders Bulletin Board].
</blockquote>

*A manufacturer's tech sheet may specifically advise against using an acid pretreatment. Always follow the tech sheets for the products you are using.

*Amateurs and [[First paint job|first-time painters]] are more likely to make errors. Phosphoric acid pretreatments must be used meticulously, and are thus not recommended for beginners.

==Specific paint and primer failures caused by phosphoric acid pretreatments==
*Bubbles of paint lifting, especially at seams.
*Epoxy cracking.

==Published epoxy primer and paint manufacturers' positions on the use of phosphoric acid pretreatments==
===Southern Polyurethanes, Inc.===
*[http://www.southernpolyurethanes.com/tech%20sheets%20new/epOXY%202006.pdf Southern Polyurethanes]:
<blockquote>
''"NEVER use SPI Epoxy over a Soda Blasted vehicle, Acid Etch/Wash Primer, Rust Converter or other Metal Treatments. NEVER!"''
</blockquote>

The owner of Southern Polyurethanes has detailed some options that '''should''' solve the phosphoric acid film problem, in [http://www.hotrodders.com/forum/ospho-factory-response-173513.html#post1235021 this post on the Hotrodders Bulletin Board].

==Use of phosphoric acid in an industrial setting==



==References==
*http://www.hotrodders.com/forum/ospho-factory-response-173513.html
*http://www.ospho.com/directions.htm
*http://www.ospho.com/images/2008%20MSDS.pdf
*http://en.wikipedia.org/wiki/Phosphoric_acid