A three-stage procedure used by R.W. Evans and Associates for new stainless and found to be the most effective is outlined below. Special note should be made that the process employs non-toxic, non-corrosive, and biodegradable substances.
Because of differing metallurgies and highly variable conditions found within each system, it is not possible to employ this sophisticated process in a standard, mechanical manner. The speficic agents and their proportions used will vary, substantially in some cases, consistent with encountered conditions. Only after inspection and preliminary testing can a determination concerning the applied process be made. Often times, testing performed during each stage will dictate changing the parameters and substances used for the remainder of the processes.
Only after the process is complete can documentation regarding the specific processes and substances that were used be generated. Documentation regarding the substances used for each system cleaned and passivated, in addition to other pertinent information, is recorded within the project log 'three-stage process', however, employs the following general steps:
1. Staged Alkaline Chelation with Detergency:
The purpose of this step is to remove dirt, debris, atmospheric dusts, and amphoteric substances such as calcium, manganese, zinc, aluminum, as well as ferric hydroxide. This stage includes use of a semi-chelants non-ionic surfactants primary chelating agents, silicon complexors and detergents in double duty as buffers in a multi-stage application.
2. Staged Acidic Chelation with Applied Reductants:
Free iron, excess manganese, iron oxides, extraneous nickel and its oxides, and heat tint phase within the HAZ of welds, and other contaminants as subsurface/subsurface (delta) Ferrite are removed. Included in this complex are chelating agents, reductants and non-ionic surfactants in a multi-stage mildly acidic comprehensive application.
3. Passivation
The final step removes the remaining traces of a certain iron compound in ppb from the dynamic sub-surface and initiates the viable "passive film." This stage includes a very specialized exact chelating complex together with unique penetrating surfactants.
The applied analyses used are primarily site spectrophotometry and specific ion. The phases are continued until analyses demonstrate extractable contaminant(s) curve stability plus additional time for substantiation of same.
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