Passivation of Corrosion Resistant Steels
|Publication Date:||1 March 2018|
This specification covers the requirements for a process to assure removal of free iron or other less noble contaminants from the surfaces of corrosion resistant steel parts.
The processes defined in this specification have been used typically to dissolve tramp metallic elements from the surfaces of corrosion resistant steels to improve their corrosion resistance, but usage is not limited to such applications.
Passivation methods covered by this specification are as follows:
Method 1 - Passivation in Nitric Acid
Method 2 - Passivation in Citric Acid
Either method may be used unless a method is specified by purchaser. Where QQ-P-35 or AMS-QQ-P-35 is specified, Method 1 shall be used unless Method 2 is authorized by the cognizant engineering organization.
The following types may be specified for Method 1:
Type 1 Low Temperature Nitric Acid with Sodium Dichromate
Type 2 Medium Temperature Nitric Acid with Sodium Dichromate
Type 3 High Temperature Nitric Acid with Sodium Dichromate
Type 4 40% Nitric Acid for Free Machining Steels
Type 5 Anodic, for High Carbon Martensitic Steels
Type 6 Low Temperature Nitric Acid
Type 7 Medium Temperature Nitric Acid
Type 8 Medium Temperature, High Nitric Acid Concentration
Where no type is specified, the processor may use any of the listed types that meet the requirements given herein.
Passivation verification classes are as follows:
The following types of parts shall be selected for testing in accordance with 4.3.1
Fasteners, including nuts, bolts, washers, rivets and related hardware where a test frequency is not defined in the procurement documents.
Standard parts defined by drawings labeled AN, MS, NAS or similar where frequency of test is not otherwise defined.
When specified by purchaser.
Frequency of corrosion testing shall be one part per lot.
Frequency of testing shall be on a periodic basis.
Parts for which AMS-QQ-P-35 or QQ-P-35 is specified shall be acceptance tested in accordance with 4.3.4.
When no class is specified and neither 18.104.22.168 nor 22.214.171.124 apply, class 2 shall apply.
Safety - Hazardous Materials
While the materials, methods, applications, and processes described or referenced in this specification may involve the use of hazardous materials, this specification does not address the hazards which may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved.