PASSIVATION2019-03-18T15:19:00-04:00

Passivation of Stainless Steel: Nitric & Citric

H&W Global offers high quality, cost effective passivation of stainless steel parts or components.

There are many options available in passivating metals. At H&W, we offer both nitric and citric acid passivation, with variations in process time, acid temperature and concentration to meet our customer specifications.

Stainless steel has a natural oxide “passive” layer that protects it from corrosion. However when stainless steel is machined, cut or assembled, the stainless surface is often contaminated by the oils and greases used in the fabrication process. If not removed, this contamination will eventually lead to corrosion. 

Contaminants are removed by cleaning the metal, and then using acid, usually nitric acid, to remove free iron from the surface. Slowly and naturally a “passive” layer is developed on the surface of the stainless steel, and it is once un-reactive. This passive layer is not visible as it is only a few molecules thick, but it provides a barrier to prevent oxygen and moisture from reaching the iron underneath. If oxygen were to reach the iron, it would oxidize – or rust – turning a yellowish or orange-red color. Over time rust would weaken the metal.

The commonly used nitric acid passivation process can quickly dissolve all the iron compounds and other trace metals on the surface and help to recreate the passive layer at the same time.  The results are controlled by the time in the acid, the temperature of the acid, and the concentration of the acid – Time, Temp, and Conc. 

At H&W, we have years of successful passivation experience. We passivate to standards ranging from military specs to aerospace material specs to unique customer developed specs.  There are many options available depending on the alloy used. We can help customers develop their own standard to accommodate their particular metal component or product.

If you have passivation questions,or  if you would like a quote on a particular project, please contact our customer services experts.

H&W’s Passivation Services include the following steps: racking, cleaning, etching, deoxidizing, painting, anodizing, dying, sealing, unracking, rinsing and  packaging. Each can be customized for your specific metal and desired coating type.

Passivation at H&W Global meets or exceeds stringent military standards, including:

ASTM-A380
ASTM-A967
QQ-P-35
AMS-2700

Ask H&W Global
about Passivation:

Why is passivation even needed when using stainless steel that is already corrosion resistant?2018-10-16T10:46:20-04:00

Stainless steel is indeed corrosion resistant, but the surface is contaminated by machining, fabricating and general handling. The natural protective layer has been compromised.

How thick is a passivation coating?2018-10-16T10:47:37-04:00

Almost negligible, invisible and only a few molecules thick.

Can you see a passivation coating? What color is it?2018-10-16T10:48:36-04:00

No, passivation is a clear coating

Is nitric acid the only passivation choice?2018-10-16T10:50:55-04:00

Citric acid passivation is also available at H&W. Citric provides a coating as good or better than the nitric acid solution.

How may we help you?

Custom Masking
Custom Graphics
Laser Engraving
Threaded Inserts
Assembly, Kitting
Custom Packaging