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Paint adhesion to Mg (AZ91D) Thixomolding part - what are the factors

2005

Hi,

I have problem of keeping the production of the paint within the spec of preformance.
I'm mainly speaking on 2 issues:
1. Adhesion test (post thermal+humidity of +65C/90 % R.H for 48 hours) .
2. resistance to sun tan lotion , which imitates to some extent the oils that this part may come in cotact during it's life.

I know how to control the process of the painting + passivation (passivation is "Shadan" passivation), still there is a large variance between 2 lots subjected to the same test.

My Question is (ignoring the paint material):

1. Are there inner Magnesium material cause effects? I.E, is the Mg casting still active post passivation and does this contribute to the paint's reduced preformance?

2. Is there a minimum time period between passivation and painting process?

Thank you in advance,

Yonatan Kemelman
Mechanical Engineer in a Telecommunication Company - Tel Aviv, Israel

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2005

Yonatan, I do not know what is "Shadan" process, but it does not look like something for magnesium. 48 hours is very low requirement.
We already many years work with magnesium and we have coating line in Israel as well supply chemicals to other countries.
You can contact us by Chemetall or by Israeli Magnesium Users Association (there know me very well)

Ilya Ostrovsky
- Frankfurt/Main Germany, Alonim Israel

Magnesium is not amenable to the normal "passivation". Magnesium is way too active. That said, I do not have any constructive suggestions other than trying the same process with AZ91HP.

Pat Reid
- Costa Mesa, California, USA
2005